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Astronomy Picture of the Day |
APOD: 2023 May 15 – M16: Eagle Nebula Deep Field
Explanation:
From afar, the whole thing looks like an
eagle.
A closer look at the
Eagle Nebula,
however, shows the
bright
region is actually a window into the center of a larger dark shell of
dust.
Through this window, a brightly-lit
workshop appears
where a whole open cluster
of stars is being formed.
In this cavity,
tall
pillars and
round globules of dark dust and cold
molecular gas
remain where stars are still forming.
Already visible are several young
bright blue stars
whose light and winds are burning away and pushing back the
remaining filaments
and walls of gas and dust.
The Eagle emission nebula,
tagged M16, lies about 6500
light years away, spans about 20 light-years,
and is visible with
binoculars
toward
the constellation of the Serpent
(Serpens).
This picture
involved
long and deep exposures and combined
three specific emitted colors emitted by
sulfur (colored as yellow),
hydrogen (red), and
oxygen (blue).
APOD: 2023 May 1 – Carina Nebula North
Explanation:
The Great Carina Nebula
is home to strange stars and iconic nebulas.
Named for its
home constellation, the huge star-forming region is larger and brighter than the
Great Orion Nebula
but less well known because it is so far south -- and because so
much of humanity lives so far north.
The featured image
shows in great detail the northernmost part of the
Carina Nebula.
On the bottom left is the
Gabriela Mistral
Nebula consisting of an
emission nebula
of glowing gas (IC 2599) surrounding the small open cluster of stars
(NGC 3324).
Above the image center is the larger star cluster
NGC 3293,
while to its right is the emission nebula Loden 153.
The most famous occupant of the
Carina Nebula,
however, is not shown.
Off the image to the lower right is the bright, erratic, and doomed star known as
Eta Carinae --
a star once
one of the brightest stars in the sky and now predicted to explode in a
supernova sometime in the next few million years.
APOD: 2023 January 3 – Kembles Cascade of Stars
Explanation:
This line of stars is real.
A little too faint to see with the unaided eye,
Kemble’s Cascade of stars
inspires awe when seen with binoculars.
Like the
Big Dipper though, Kemble’s Cascade is an
asterism, not a
constellation.
The asterism is visible in the northern sky toward the long-necked constellation of the
Giraffe
(Camelopardalis).
This string of about 20 unrelated
stars, each of similar brightness,
spans over five times the
angular width of the
full moon.
Stretching diagonally from the upper left to the lower right,
Kemble's Cascade was popularized last century by astronomy enthusiast
Lucian Kemble.
The bright object near the top left of the image is the relatively compact
Jolly Roger open cluster of stars, officially designated as
NGC 1502.
APOD: 2022 August 8 - The Lagoon Nebula without Stars
Explanation:
Ridges of glowing interstellar gas and
dark dust clouds inhabit the
turbulent, cosmic depths of the
Lagoon Nebula.
Also known as
M8, the bright star forming region is about
5,000 light-years distant.
But it still makes for a popular stop on
telescopic tours of
the constellation Sagittarius, toward the center of
our Milky Way Galaxy.
Dominated by the telltale red emission of ionized hydrogen atoms
recombining with stripped electrons,
this stunning, deep view of the Lagoon is nearly
100 light-years across.
Right of center, the bright, compact, hourglass
shape is gas ionized and sculpted by energetic radiation
and extreme stellar winds from a
massive young star.
In fact, although
digitally removed from the
featured image,
the many bright stars of open cluster NGC 6530
drift within the nebula,
just formed in
the Lagoon several million years ago.
APOD: 2022 April 30 - M44: The Beehive Cluster
Explanation:
A mere 600 light-years away,
M44 is one of the closest
star clusters to our solar system.
Also known as the
Praesepe
or the Beehive cluster its stars
are young though, about 600 million years old compared to our Sun's
4.5 billion
years.
Based on similar ages and motion through space, M44 and the
even closer Hyades star cluster in Taurus
are thought to have
been born together in the same large molecular cloud.
An open cluster
spanning some 15 light-years, M44 holds 1,000 stars or so
and covers about 3 full moons (1.5 degrees) on the
sky in the constellation Cancer.
Visible to the unaided eye, M44 has been recognized since antiquity.
Described as a faint cloud or celestial mist long before
being included as the 44th entry in
Charles Messier's
18th century catalog, the cluster was not resolved into its individual
stars until telescopes were available.
A popular target for modern, binocular-equipped sky gazers,
the cluster's few
yellowish tinted, cool,
red giants are scattered
through the field of its brighter hot blue main sequence
stars in this
telescopic group snapshot.
Dramatic
diffraction spikes
highlighting the brighter cluster members
were created with string crossed in front of the telescope's objective
lens.
APOD: 2022 February 18 - Three Clusters in Puppis
Explanation:
Galactic or
open star clusters
are young.
The swarms of stars are born together near the plane of the Milky Way,
but their numbers
steadily dwindle
as cluster members are
ejected by galactic tides and gravitational interactions.
Caught in
this telescopic frame
over three degrees across are three
good examples of galactic star clusters,
seen toward the southern sky's nautical constellation
Puppis.
Below and left, M46 is
some 5,500 light-years in the distance.
Right of center
M47 is
only 1,600 light-years away and
NGC 2423 (top) is about 2500 light-years distant.
Around 300 million years young M46
contains a few hundred stars in a region about 30 light-years
across.
Sharp eyes can spot a planetary nebula,
NGC 2438,
at about 11 o'clock against the M46 cluster stars.
But that nebula's
central star
is billions of years old, and
NGC 2438 is likely a foreground object only by chance
along the line of sight to youthful M46.
Even younger, aged around 80 million years, M47 is a
smaller and looser star cluster spanning about 10 light-years.
Star cluster NGC 2423 is pushing about 750 million years
in age though.
NGC 2423 is known to harbor an extrasolar planet,
detected orbiting one
of its red giant stars.
APOD: 2022 February 14 - In the Heart of the Heart Nebula
Explanation:
What excites the Heart Nebula?
First, the large emission nebula dubbed
IC 1805 looks, in whole, like a human heart.
Its shape perhaps fitting of the
Valentine's Day,
this heart glows brightly in red light
emitted by its most prominent element:
excited
hydrogen.
The red glow and the larger shape are all created by a
small group of stars near the
nebula's center.
In the heart of the
Heart
Nebula are young stars from the open star cluster
Melotte 15
that are eroding away several
picturesque dust pillars with their energetic light and winds.
The open cluster of stars contains a few
bright stars nearly 50 times the mass of our Sun,
many dim stars only a fraction of the mass of our Sun, and an
absent microquasar
that was expelled millions of years ago.
The Heart Nebula
is located about 7,500 light years away toward the
constellation
of the
mythological Queen of Aethiopia
(Cassiopeia).
APOD: 2022 January 31 - Carina Nebula North
Explanation:
The Great Carina Nebula
is home to strange stars and iconic nebulas.
Named for its
home constellation, the huge star-forming region is larger and brighter than the
Great Orion Nebula
but less well known because it is so far south -- and because so
much of humanity lives so far north.
The featured image
shows in great detail the northern-most part of the
Carina Nebula.
Visible nebulas include the semi-circular filaments surrounding the active
star Wolf-Rayet 23 (WR23) on the far left.
Just left of center is the
Gabriela Mistral
Nebula consisting of an
emission nebula
of glowing gas (IC 2599) surrounding the small open cluster of stars
(NGC 3324).
Above the image center is the larger star cluster
NGC 3293,
while to its right is the relatively faint emission nebula designated Loden 153.
The most famous occupant of the
Carina Nebula,
however, is not shown.
Off the image to the lower right is the bright, erratic, and doomed star star known as
Eta Carinae --
a star once
one of the brightest stars in the sky and now predicted to explode in a
supernova sometime in the next few million years.
APOD: 2021 October 8 - The Double Cluster in Perseus
Explanation:
This pretty starfield spans about three full moons (1.5 degrees)
across the heroic northern constellation of
Perseus.
It holds the famous
pair of open star clusters,
h and Chi Persei.
Also cataloged as
NGC 869 (top) and NGC 884,
both clusters are about 7,000 light-years away and
contain stars much younger and hotter than the Sun.
Separated by only a few hundred light-years, the clusters are
both 13 million years young
based on
the ages of
their individual
stars,
evidence that they were likely a product of the same
star-forming region.
Always a rewarding
sight in binoculars,
the Double Cluster is
even visible to the unaided eye from
dark locations.
But a shroud of guitar strings was used to produce
diffraction spikes
on the colorful stars imaged in this vibrant telescopic view.
APOD: 2021 September 25 - The Bubble and the Star Cluster
Explanation:
To the eye,
this cosmic composition
nicely balances the
Bubble Nebula at the right with open star cluster M52.
The pair would be lopsided on other scales, though.
Embedded in a complex of
interstellar dust
and gas and blown by the winds from a single, massive
O-type star,
the Bubble Nebula, also known as NGC 7635, is a
mere 10 light-years wide.
On the other hand,
M52 is a rich open
cluster of around a thousand stars.
The cluster is about 25 light-years across.
Seen toward the northern boundary
of Cassiopeia, distance estimates
for the Bubble Nebula and associated cloud complex are around
11,000 light-years, while
star cluster M52
lies nearly 5,000 light-years away.
The wide telescopic field of view spans about 1.5 degrees on the sky
or three times the apparent size of a full Moon.
APOD: 2021 February 21 - NGC 2244: A Star Cluster in the Rosette Nebula
Explanation:
In the heart of the
Rosette Nebula lies a bright
open cluster
of stars that lights up the nebula.
The stars of NGC 2244 formed from the surrounding gas only a few million years ago.
The featured image
taken in January using multiple exposures and very specific colors of
Sulfur (shaded red),
Hydrogen (green), and
Oxygen (blue),
captures the central region in tremendous detail.
A hot wind of particles streams away from the cluster
stars and contributes to an already
complex menagerie of gas and
dust filaments while slowly evacuating the cluster center.
The Rosette Nebula's
center measures about 50 light-years across, lies about 5,200 light-years away,
and is visible with binoculars towards the constellation of
the Unicorn
(Monoceros).
APOD: 2021 February 14 - Long Stem Rosette Nebula
Explanation:
Would the
Rosette Nebula
by any other
name look as sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of
this
flowery emission nebula,
at the top of the image, atop a
long stem of glowing hydrogen gas.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to
glow.
The Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of
the Unicorn (Monoceros).
APOD: 2020 November 18 - A Double Star Cluster in Perseus
Explanation:
Most star clusters are singularly impressive.
Open clusters NGC 869 and NGC 884,
however, could be considered doubly impressive.
Also known as "h and chi Persei", this unusual
double cluster, shown above, is bright enough to be seen from a
dark location without even
binoculars.
Although their discovery surely predates
recorded history, the Greek astronomer
Hipparchus
notably cataloged the
double cluster.
The clusters are over 7,000 light years distant toward the
constellation
of Perseus,
but are separated by only hundreds of light years.
In addition to being
physically close together,
the clusters' ages
based on
their individual stars are similar - evidence that both
clusters were likely a product of the same
star-forming region.
APOD: 2020 September 9 - Pleiades: The Seven Sisters Star Cluster
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it as large and clear as this.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The featured exposure covers a
sky area several times the size of the full
moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only
six of the sister stars visible to the unaided eye.
The actual number of
Pleiades stars visible,
however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2020 September 4 - The Wizard Nebula
Explanation:
Open star cluster NGC 7380 is still embedded in
its natal cloud
of interstellar gas and dust popularly known as the
Wizard Nebula.
Seen on the left, with foreground and background stars
along the
plane of our Milky Way galaxy
it lies some 8,000 light-years distant, toward the constellation
Cepheus.
In apparent size on the sky, a full moon would cover
the 4 million year
young
cluster and associated nebula, normally
much too faint to be seen by eye.
Made with telescope and camera firmly planted on Earth,
the image reveals multi light-year sized shapes and structures
of cosmic gas and dust within the Wizard though, in a color palette made
popular in Hubble
Space Telescope images.
Recorded with narrowband filters, the visible wavelength light
from the nebula's hydrogen, oxygen, and sulfur atoms is transformed
into green, blue, and red colors in the
final digital composite.
APOD: 2020 August 30 - NGC 6357: Cathedral to Massive Stars
Explanation:
How massive can a normal star be?
Estimates made from distance, brightness and standard
solar models had given one star in the
open cluster Pismis 24
over 200 times the mass of our
Sun, making it one of the most massive stars known.
This star is the brightest object
located just above the gas front in the
featured image.
Close inspection of
images taken with the
Hubble Space Telescope,
however, have shown that Pismis 24-1 derives its brilliant luminosity
not from a single star but from
three at least.
Component stars would still remain near 100 solar masses,
making them among the more
massive stars currently on record.
Toward the bottom of the image,
stars
are still forming in the associated
emission nebula
NGC 6357.
Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be
breaking out
and illuminating a
spectacular cocoon.
APOD: 2020 August 6 - Messier 20 and 21
Explanation:
The beautiful Trifid Nebula,
also known as Messier 20, is easy
to
find with a small telescope in the nebula rich constellation
Sagittarius.
About 5,000 light-years away, the colorful study in
cosmic contrasts shares
this well-composed, nearly 1 degree wide field with
open star cluster
Messier 21
(right).
Trisected by dust lanes
the Trifid itself is about 40 light-years across and
a mere 300,000 years old.
That makes it one of the
youngest star
forming
regions in our sky,
with newborn and embryonic stars embedded in its
natal dust and gas clouds.
Estimates of the distance to open star cluster M21 are similar to M20's,
but though they share this gorgeous telescopic skyscape
there is no apparent connection between the two.
In fact, M21's stars are much older, about 8 million
years old.
APOD: 2020 January 30 - Two Clusters and a Comet
Explanation:
This lovely starfield spans some four full moons (about 2 degrees) across the
heroic northern constellation of
Perseus.
In telescopic exposures made during the nights of January 24, 26, and 28
it holds the famous pair of open or galactic star clusters h and Chi Persei
with comet PanSTARRS (C/2017 T2) captured each night as it swept left to right across the field of view.
Also cataloged as
NGC
869 (right) and NGC 884,
both star clusters are about 7,000 light-years away and
contain stars much younger and hotter than the Sun.
Separated by only a few hundred light-years, the clusters are
both 13 million years young
based on
the ages of
their individual
stars,
evidence that they were likely a product of the same
star-forming region.
Discovered in 2017 while still beyond the orbit of Saturn, Comet PanSTARRs is
a new visitor to
the inner solar system and just over 13 light-minutes from planet Earth.
Always a rewarding
sight in binoculars,
the Double Cluster is
even visible to the unaided eye from
dark locations.
C/2017 T2
could remain a telescopic comet though.
One of the brightest
comets anticipated in 2020
it makes its closest approach to the Sun in early May.
APOD: 2020 January 22 - The Hyades Star Cluster
Explanation:
It is the closest cluster of stars to the Sun.
The Hyades
open cluster
is bright enough to have been remarked on even thousands of years ago,
yet is not as bright or compact as the
nearby Pleiades (M45) star cluster.
Pictured here is a particularly deep image of
the Hyades which has brings out vivid
star colors and faint coincidental nebulas.
The brightest star in the field is yellow
Aldebaran,
the eye of the bull toward the
constellation of Taurus.
Aldebaran, at 65
light-years away, is now known to be unrelated to the
Hyades cluster,
which lies about 150 light-years away.
The central
Hyades stars
are spread out over about 15 light-years.
Formed about 625 million years ago,
the Hyades likely shares a common origin with the
Beehive cluster (M44), a naked-eye open star cluster toward the
constellation of Cancer, based on
M44's motion
through space and remarkably similar age.
APOD: 2019 December 30 - Messier 20 and 21
Explanation:
The beautiful Trifid Nebula,
also known as Messier 20, is easy
to
find with a small telescope in the nebula rich constellation
Sagittarius.
About 5,000 light-years away, the colorful study in
cosmic contrasts shares
this
well-composed, nearly 1 degree wide field with
open star cluster
Messier 21
(top left).
Trisected by dust lanes
the Trifid itself is about 40 light-years across and
a mere 300,000 years old.
That makes it one of the
youngest star
forming
regions in our sky,
with newborn and embryonic stars embedded in its
natal dust and gas clouds.
Estimates of the distance to open star cluster M21 are similar to M20's,
but though they share this gorgeous telescopic skyscape
there is no apparent connection between the two.
In fact, M21's stars are much older, about 8 million
years
old.
APOD: 2019 October 13 - A Stellar Jewel Box: Open Cluster NGC 290
Explanation:
Jewels don't shine this bright -- only stars do.
Like gems in a jewel box, though, the stars of
open cluster
NGC 290 glitter in a
beautiful display of brightness and color.
The photogenic cluster,
pictured here,
was captured in 2006 by the orbiting
Hubble Space Telescope.
Open clusters of stars are younger, contain few stars,
and contain a much higher fraction of blue stars than do
globular clusters of stars.
NGC 290 lies about 200,000
light-years
distant in a neighboring galaxy called the
Small Cloud of Magellan (SMC).
The open cluster contains hundreds of stars
and spans about 65 light years across.
NGC 290
and other open clusters are good laboratories for studying how
stars of different masses evolve,
since all the open cluster's stars were born at about the same time.
APOD: 2019 September 11 - IC 1805: The Heart Nebula
Explanation:
What energizes the Heart Nebula?
First, the large emission nebula dubbed
IC 1805 looks, in whole, like a human heart.
The nebula glows brightly in red light
emitted by its most prominent element:
hydrogen.
The red glow and the larger shape are all powered by a
small group of stars near the
nebula's center.
In the center of the
Heart Nebula are young stars from the open star cluster
Melotte 15
that are eroding away several picturesque
dust pillars with their
energetic light and winds.
The open cluster of stars contains a few
bright stars nearly 50 times the mass of our
Sun,
many dim stars only a fraction of the mass of our Sun, and an
absent microquasar
that was expelled millions of years ago.
The Heart Nebula is located about 7,500 light years away toward the
constellation
of Cassiopeia.
Coincidentally, a small meteor was captured in the foreground during imaging
and is visible above the dust pillars.
At the top right is the companion
Fishhead Nebula.
APOD: 2019 September 1 - M45: The Pleiades Star Cluster
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it as dusty as this.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The featured exposure took over 12 hours and covers a
sky area several times the size of the full
moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye.
The actual number of
Pleiades stars visible, however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2019 August 30 - NGC 7129 and NGC 7142
Explanation:
This wide-field
telescopic image looks toward the constellation
Cepheus
and an intriguing visual pairing of dusty
reflection nebula
NGC 7129 (right) and
open star
cluster NGC 7142.
The two appear separated by only half a degree on the sky,
but they actually lie at quite different distances.
In the foreground,
dusty nebula NGC 7129
is about 3,000 light-years distant, while open cluster
NGC 7142 is likely over
6,000 light-years away.
In fact, pervasive and clumpy foreground dust clouds in
this region redden the light from NGC 7142,
complicating astronomical
explorations of the cluster.
Still, NGC 7142 is thought to be an
older open star cluster, while
the bright stars embedded in NGC 7129 are perhaps a few million
years young.
The telltale reddish crescent shapes around NGC 7129 are associated with
energetic jets streaming away from newborn stars.
APOD: 2019 May 28 - Stars, Dust, and Gas near NGC 3572
Explanation:
Star formation can be colorful.
This chromatic cosmic portrait features glowing gas and dark dust near some recently formed stars of
NGC 3572,
a little-studied star cluster near the
Carina Nebula.
Stars from NGC 3572 are visible near the bottom of the image, while the expansive gas cloud above is likely what remains of their formation nebula.
The image's striking hues were created by featuring specific colors emitted by hydrogen, oxygen, and sulfur, and
blending them
with images recorded through broadband filters in red, green, and blue.
This nebula near NGC 3572 spans about 100
light years
and lies about 9,000 light years away
toward
the southern constellation of the Ship's Keel
(Carina).
Within a few million years the pictured gas will likely disperse, while
gravitational encounters
will likely disperse the cluster stars over about a billion years.
APOD: 2019 May 14 - Young Star Cluster Trumpler 14 from Hubble
Explanation:
Why does star cluster Trumpler 14 have so many bright stars?
Because it is so young.
Many cluster stars have formed only in the past
5 million years and are so hot they emit
detectable X-rays.
In older star clusters,
most stars this young have already died -- typically
exploding in a supernova -- leaving behind stars that are fainter and redder.
Trumpler 14 spans about 40 light years and lies about 9,000
light years away on the edge of the famous
Carina Nebula.
A discerning eye can spot two unusual objects in
this detailed 2006 image of Trumpler 14 by the
Hubble Space Telescope.
First, a dark cloud
just left of center may be a planetary system trying to
form before being destroyed by the
energetic winds of
Trumpler 14's massive stars.
Second is
the arc
at the bottom left, which one hypothesis holds is the
supersonic shock wave
of a fast star ejected 100,000 years ago from a
completely different star cluster.
APOD: 2019 March 16 - NGC 3324 in Carina
Explanation:
This
bright cosmic cloud
was sculpted by stellar
winds and radiation from the hot young stars
of open cluster NGC 3324.
With dust clouds in silhouette against its glowing atomic gas, the
pocket-shaped
star-forming region actually spans about 35 light-years.
It lies some 7,500 light-years away toward the nebula rich
southern constellation
Carina.
A composite of narrowband image data, the telescopic view
captures the characteristic emission from ionized sulfur, hydrogen,
and oxygen atoms mapped to red, green, and blue hues in the
popular Hubble Palette.
For some, the celestial landscape of bright ridges of
emission bordered by cool, obscuring
dust along
the right side create a recognizable face in profile.
The region's popular name is the
Gabriela
Mistral Nebula for the Nobel Prize winning Chilean poet.
APOD: 2018 November 22 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as NGC 281
and you might miss the stars of open cluster
IC 1590.
Still, formed
within
the nebula that cluster's young, massive stars
ultimately power the pervasive nebular glow.
The eye-catching shapes looming in
this
portrait of NGC 281 are sculpted dusty columns and dense
Bok globules
seen in silhouette, eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Playfully called
the Pacman Nebula because of its overall shape,
NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This sharp composite image was made through
narrow-band filters.
It combines emission from the nebula's hydrogen and oxygen
atoms to synthesize red, green, and blue colors.
The scene spans well over 80 light-years at the estimated distance of NGC 281.
APOD: 2018 November 12 - The Lagoon Nebula is Stars, Gas, and Dust
Explanation:
The majestic
Lagoon Nebula
is filled with hot gas and the home for many young stars.
Spanning 100 light years across while lying only about 5000 light years distant, the
Lagoon Nebula is so big and bright that it
can be seen without a
telescope toward the
constellation of the Archer
(Sagittarius).
Many bright stars are visible from
NGC 6530, an
open cluster that
formed in the nebula only several million years ago.
The greater nebula, also known as
M8 and
NGC 6523,
is named "Lagoon" for the band of dust seen to the
left of the open cluster's center.
The featured image was taken in three colors with details are brought out by
light emitted by
Hydrogen.
Star formation continues in the
Lagoon Nebula as witnessed
by the many dark dust-laden
globules that exist there.
APOD: 2018 October 15 - M16: In and Around the Eagle Nebula
Explanation:
From afar, the whole thing looks like an
Eagle.
A closer look at the
Eagle Nebula,
however, shows the
bright
region is actually a window into the center of a larger dark shell of
dust.
Through this window, a brightly-lit
workshop appears
where a whole open cluster
of stars is being formed.
In this cavity
tall pillars and
round globules of dark dust and cold
molecular gas
remain where stars are still forming.
Already visible are several young
bright blue stars
whose light and winds are burning away and pushing back the
remaining filaments
and walls of gas and dust.
The Eagle emission nebula,
tagged M16, lies about 6500
light years away, spans about 20 light-years,
and is visible with
binoculars toward
the constellation of the Serpent
(Serpens).
This picture
involved over 25 hours of imaging and combines
three specific emitted colors emitted by
sulfur (colored as red),
hydrogen (yellow), and
oxygen (blue).
APOD: 2018 August 24 - Messier 20 and 21
Explanation:
The beautiful Trifid Nebula,
also known as Messier 20, is easy
to
find with a small telescope in the nebula rich constellation Sagittarius.
About 5,000 light-years away, the colorful study in
cosmic contrasts shares
this
well-composed, nearly 1 degree wide field with
open star cluster
Messier 21
(bottom right).
Trisected by dust lanes
the Trifid itself is about 40 light-years across and
a mere 300,000 years old.
That makes it one of the
youngest star
forming
regions in our sky,
with newborn and embryonic stars embedded in its
natal dust and gas clouds.
Estimates of the distance to open star cluster M21 are similar to M20's,
but though they share this gorgeous telescopic skyscape
there is no apparent connection between the two.
In fact, M21's stars are much older, about 8 million
years
old.
APOD: 2018 April 6 - NGC 3324 in Carina
Explanation:
This
bright cosmic cloud
was sculpted by stellar
winds and radiation from the hot young stars
of open cluster NGC 3324.
With dust clouds in silhouette against its glowing atomic gas, the
pocket-shaped
star-forming region actually spans about 35 light-years.
It lies some 7,500 light-years away toward the nebula rich
southern constellation
Carina.
A composite of narrowband image data, the telescopic view
captures the characteristic emission from ionized sulfur, hydrogen,
and oxygen atoms mapped to red, green, and blue hues in the
popular Hubble Palette.
For some, the celestial landscape of bright ridges of
emission bordered by cool, obscuring
dust along
the right side create a recognizable face in profile.
The region's popular name is the
Gabriela
Mistral Nebula for the Nobel Prize winning Chilean poet.
APOD: 2018 February 14 - In the Heart of the Heart Nebula
Explanation:
What's that inside the Heart Nebula?
First, the large emission nebula dubbed
IC 1805 looks, in whole, like a human heart.
It's shape perhaps fitting of the
Valentine's Day,
this heart glows brightly in red light
emitted by its most prominent element:
hydrogen.
The red glow and the larger shape are all created by a
small group of stars near the
nebula's center.
In the heart of the
Heart
Nebula are young stars from the open star cluster
Melotte 15 that are eroding away several picturesque
dust pillars with their energetic light and winds.
The open cluster of stars contains a few
bright stars nearly 50 times the mass of our Sun,
many dim stars only a fraction of the mass of our Sun, and an
absent microquasar
that was expelled millions of years ago.
The Heart Nebula is located about 7,500 light years away toward the
constellation
of the mythological Queen of Aethiopia (Cassiopeia).
APOD: 2017 November 15 - NGC 7789: Caroline's Rose
Explanation:
Found among the rich starfields of the Milky Way,
star
cluster NGC 7789 lies about 8,000 light-years away
toward the constellation Cassiopeia.
A late 18th century
deep sky discovery of astronomer
Caroline Lucretia Herschel,
the cluster is also known as Caroline's Rose.
Its flowery
visual appearance
in small telescopes is created by
the cluster's nestled complex of stars and voids.
Now estimated to be 1.6 billion years young, the
galactic or open cluster of stars also shows its age.
All the stars in the cluster were likely born
at the same time, but the brighter and more massive ones have more
rapidly exhausted the hydrogen fuel in their
cores.
These have evolved from
main sequence
stars like the Sun into the many red giant stars shown with a
yellowish cast in this lovely color composite.
Using measured color and brightness,
astronomers can model the mass and hence the age of
the cluster stars just starting to "turn off" the main sequence
and become red giants.
Over 50 light-years across,
Caroline's Rose spans about
half a degree (the angular size of the Moon) near the center of
the
wide-field telescopic image.
APOD: 2017 November 14 - The Pleiades Deep and Dusty
Explanation:
The well-known Pleiades star cluster is slowly destroying part of a passing cloud of
gas and dust.
The Pleiades
is the brightest
open cluster of stars
on Earth's sky and
can be seen from almost any northerly location with the
unaided eye.
The passing young dust cloud is thought to be part of
Gould's Belt, an
unusual ring of young star formation surrounding the Sun in the
local Milky Way Galaxy.
Over the past 100,000 years, part of
Gould's Belt
is by chance moving right through the older
Pleiades and is causing
a strong reaction between
stars and dust.
Pressure from the stars' light significantly repels
the dust in the surrounding blue
reflection nebula, with
smaller dust particles being repelled more strongly.
A short-term result is that parts of the dust cloud have become
filamentary and
stratified.
The featured deep image also captured
Comet C/2015 ER61
(PanSTARRS) on the lower left.
APOD: 2017 October 2 - Two Comets and a Star Cluster
Explanation:
Two unusual spots are on the move near the famous Pleiades star cluster.
Shifting only a small amount per night,
these spots are actually
comets
in our nearby Solar System that by chance wandered
into the field of the
light-years distant stars.
On the far left is comet
C/2017 O1 ASAS-SN, a multi-kilometer
block of evaporating ice sporting a
bright coma of surrounding gas dominated by
green-glowing carbon.
Comet ASAS-SN1
shows a slight tail to its lower right.
Near the frame center is comet
C/2015 ER61 PanSTARRS,
also a giant block of
evaporating ice,
but sporting a rather
long tail to its right.
On the upper right is
the Pleiades, an
open cluster
dominated by bright blue stars illuminating
nearby reflecting dust.
This exposure, taken about two weeks ago,
is so deep that the filamentary interstellar dust can be traced across the
entire field.
The Pleiades is visible to the
unaided eye, but it should require binoculars to
see the comets.
APOD: 2017 September 30 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as NGC 281
and you might miss the stars of open cluster
IC 1590.
Still, formed
within
the nebula that cluster's young, massive stars
ultimately power the pervasive
nebular glow.
The eye-catching shapes looming in
this
portrait of NGC 281 are sculpted columns and dense
dust globules
seen in silhouette, eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Playfully called
the Pacman Nebula because of its overall shape,
NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This sharp composite image was made through
narrow-band filters,
combining emission from the nebula's hydrogen, sulfur, and oxygen
atoms in green, red, and blue hues.
It spans over 80 light-years at the estimated distance of NGC 281.
APOD: 2017 July 4 - Celestial Fireworks: Into Star Cluster Westerlund 2
Explanation:
What if you could go right into a cluster where stars are forming?
A one-minute, time-lapse,
video visualization of just this has been made with 3D
computer modeling
of the region surrounding the star cluster
Westerlund 2, based on
images from the
Hubble Space Telescope in
visible and
infrared light.
Westerlund 2
spans about 10 light years across and lies about 20,000 light years distant toward the constellation of the Ship's Keel
(Carina).
As the
illustrative animation
begins, the greater
Gum 29 nebula
fills the screen, with the young cluster of bright stars visible in the center.
Stars zip past you as you approach the cluster.
Soon your
imaginary ship
pivots and you pass over light-year
long pillars
of interstellar gas and dust.
Strong
winds
and radiation from massive young stars destroy all but the densest nearby
dust clumps, leaving these pillars in their
shadows --
many pointing back toward the cluster center.
Last, you pass into the top of the
star cluster and survey hundreds of the
most massive stars known.
APOD: 2017 June 28 - Composite Messier 20 and 21
Explanation:
The beautiful Trifid Nebula,
also known as Messier 20, lies about 5,000 light-years away, a
colorful study in cosmic contrasts.
It shares this nearly 1 degree wide field with
open star cluster
Messier 21
(top left).
Trisected by dust lanes
the Trifid itself is about 40 light-years across and
a mere 300,000 years old.
That makes it one of the
youngest star
forming regions in our sky, with newborn and embryonic stars embedded
in its
natal dust and gas clouds.
Estimates of the distance to open star cluster M21 are similar to M20's,
but though they share this gorgeous telescopic skyscape
there is no apparent connection between the two.
M21's stars are much older, about 8 million
years
old.
M20 and M21 are easy
to
find with even a small telescope in the nebula rich constellation
Sagittarius.
In fact, this well-composed scene is a
composite from two different telescopes.
Using narrowband data it blends a high resolution image of M20 with a
wider field image extending to M21.
APOD: 2017 June 20 - The Massive Stars in Westerlund 1
Explanation:
Star cluster Westerlund 1 is home to some of the largest and most massive stars known.
It is headlined by the star
Westerlund 1-26,
a red supergiant star so big that if placed in the center of
our Solar System, it would extend out past the orbit of
Jupiter.
Additionally, the young star cluster is home to 3 other
red supergiants,
6 yellow hypergiant stars,
24 Wolf-Rayet stars,
and several even-more unusual stars that continue to be studied.
Westerlund 1 is relatively close-by for a star cluster at a distance of 15,000
light years,
giving
astronomers
a good laboratory to study the development of massive stars.
The featured image
of Westerlund 1 was taken by the
Hubble Space Telescope toward the southern
constellation of the
Altar (Ara).
Although presently classified as a "super"
open cluster,
Westerlund 1 may evolve into a low mass
globular cluster
over the next billion years.
APOD: 2017 May 25 - Star Cluster, Spiral Galaxy, Supernova
Explanation:
A cosmic snapshot from May 19,
this colorful telescopic field of view spans about 1 degree
or 2 full moons on the sky.
Spiky in appearance, foreground Milky Way stars are scattered
toward the royal constellation
Cepheus while stars
of open cluster NGC 6939 gather about 5 thousand light-years in the distance
near the top of the frame.
Face-on spiral
galaxy NGC 6946 is toward the lower left nearly
22 million light-years away.
The helpful red lines identify recently discovered
supernova
SN 2017eaw, the death explosion of a massive star nestled
in the galaxy's bluish spiral arms.
In fact
in the last 100 years, 10 supernovae have been discovered in NGC 6946.
By comparison, the average rate of supernovae in our Milky Way is about 1
every 100 years
or so.
Of course, NGC 6946 is also known as
The Fireworks Galaxy.
APOD: 2017 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula
by any other
name look as sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of
this
flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to
glow.
The Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of
the Unicorn
(Monoceros).
APOD: 2016 November 6 - Starburst Cluster in NGC 3603
Explanation:
A mere 20,000 light-years from the Sun lies
NGC 3603,
a resident of the nearby Carina spiral arm of our
Milky Way
Galaxy.
NGC 3603 is well known to astronomers as
one of the Milky Way's largest star-forming regions.
The central open star cluster contains thousands of stars
more massive than
our Sun, stars that likely formed only
one or two million years ago in a single burst of star formation.
In fact,
nearby NGC 3603 is thought to contain a convenient
example of the massive star clusters that
populate much more distant
starburst
galaxies.
Surrounding
the cluster
are natal clouds of glowing
interstellar gas and obscuring dust, sculpted by energetic
stellar radiation and winds.
Recorded by
the Hubble Space Telescope,
the image
spans about 17 light-years.
APOD: 2016 November 4 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as NGC 281
and you might miss the stars of open cluster
IC 1590.
Still, formed
within
the nebula that cluster's young, massive stars
ultimately power the pervasive
nebular glow.
The eye-catching shapes looming in
this
portrait of NGC 281 are sculpted columns and dense
dust globules
seen in silhouette, eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Playfully called
the Pacman Nebula because of its overall shape,
NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This sharp composite image was made through
narrow-band filters,
combining emission from the nebula's hydrogen, sulfur, and oxygen
atoms in green, red, and blue hues.
It spans over 80 light-years at the estimated distance of NGC 281.
APOD: 2016 October 19 - M45: The Pleiades Star Cluster
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it as dusty as this.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars even from the heart of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The featured image was a long duration exposure taken last month
from Namibia and covers a
sky area many times the size of the full
moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye.
The actual number of visible
Pleiades stars, however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2016 March 27 - NGC 6357: Cathedral to Massive Stars
Explanation:
How massive can a normal star be?
Estimates made from distance, brightness and standard
solar models had given one star in the
open cluster Pismis 24
over 200 times the mass of our
Sun, making it one of the most massive stars known.
This star is the brightest object
located just above the gas front in the
featured image.
Close inspection of
images taken with the
Hubble Space Telescope,
however, have shown that Pismis 24-1 derives its brilliant luminosity
not from a single star but from
three at least.
Component stars would still remain near 100 solar masses,
making them among the more
massive stars currently on record.
Toward the bottom of the image,
stars
are still forming in the associated
emission nebula
NGC 6357.
Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be
breaking out
and illuminating a
spectacular cocoon.
APOD: 2016 January 5 - The Lagoon Nebula in Hydrogen Sulfur and Oxygen
Explanation:
The majestic
Lagoon Nebula
is filled with hot gas and the home for many young stars.
Spanning 100 light years across while lying only about 5000 light years distant, the
Lagoon Nebula is so big and bright that
it can be
seen without a
telescope toward the
constellation of the Archer
(Sagittarius).
Many bright stars are visible from
NGC 6530, an
open cluster that
formed in the nebula only several million years ago.
The greater nebula, also known as
M8 and NGC 6523,
is named "Lagoon" for the band of dust seen to the
right of the open cluster's center.
The featured image was taken in the light emitted by
Hydrogen (shown in brown),
Sulfur (red), and
Oxygen (blue)
and displayed in
enhanced color.
The featured picture is a newly processed panorama of
M8, capturing twice the diameter of the Full Moon.
Star formation continues in the
Lagoon Nebula as witnessed by the many
globules that exist there.
APOD: 2015 December 30 - The Fox Fur Nebula
Explanation:
This interstellar
canine is formed of cosmic
dust and gas interacting
with the energetic light and
winds from hot young stars.
The shape, visual texture, and color, combine to give the region
the popular name
Fox Fur Nebula.
The characteristic blue glow on the left is
dust reflecting light
from the bright star
S Mon,
the bright star just below the top edge of
the featured image.
Textured red and black areas are a combination of the cosmic dust and reddish emission from
ionized hydrogen gas.
S Mon is part of a young
open cluster of stars,
NGC 2264,
located about 2,500
light years away toward the
constellation of the Unicorn
(Monoceros).
APOD: 2015 October 27 - Bright from the Heart Nebula
Explanation:
What's that inside the Heart Nebula?
First, the large emission nebula dubbed
IC 1805 looks, in whole, like a human heart.
The nebula glows brightly in red light
emitted by its most prominent element:
hydrogen.
The red glow and the larger shape are all created by a
small group of stars near the
nebula's center.
In the center of the Heart Nebula are young stars from the open star cluster
Melotte 15 that are eroding away several picturesque
dust pillars with their energetic light and winds.
The open cluster of stars contains a few
bright stars nearly 50 times the mass of our Sun,
many dim stars only a fraction of the mass of our Sun, and an
absent microquasar
that was expelled millions of years ago.
The Heart Nebula is located about 7,500 light years away toward the
constellation
of Cassiopeia.
At the top right is the companion
Fishhead Nebula.
APOD: 2015 August 26 - Collinder 399: The Coat Hanger
Explanation:
Is this coat hanger a star cluster or an asterism?
This
cosmic hang-up has been debated over much of last century,
as astronomers wondered whether
this binocular-visible object is
really a physically associated
open cluster or a
chance projection.
Chance star projections are known as
asterisms, an example of which is the popular
Big Dipper.
Recent precise measurements from different vantage points in the Earth's orbit around the Sun
have uncovered discrepant angular shifts indicating that the
Coat Hanger
is better described as an
asterism.
Known more formally as
Collinder 399,
this bright stellar grouping is wider than the
full moon and lies in the
constellation of the
Fox
(Vulpecula).
APOD: 2015 June 17 - M45: The Pleiades Star Cluster
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it as dusty as this.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The featured exposure took over 12 hours and covers a
sky area several times the size of the full
moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye.
The actual number of
Pleiades stars visible, however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2015 June 8 - The Milky Way over the Temple of Poseidon
Explanation:
What's that glowing in the distance?
Although it may look like a
lighthouse, the rays of light near the horizon actually emanate from the
Temple of Poseidon at
Cape Sounion,
Greece.
Some temple
lights are even reflected in the
Aegean Sea in the foreground.
Although meant to be a monument to the sea, in this image,
the temple's lights seem to be pointing out locations on the sky.
For example, the wide ray toward the right fortuitously points toward the
Lagoon Nebula in the central band of our
Milky Way, which runs diagonally down the image from the upper left.
Also, the nearly vertical beam seems to point toward the star clouds near the direction of the
Wild Duck open cluster of stars.
The featured image was taken less than three weeks ago.
APOD: 2015 April 17 - M46 Plus Two
Explanation:
Galactic or
open star clusters
are young.
These swarms of stars are born together near the plane of the Milky Way,
but their numbers steadily dwindle as cluster members are
ejected by galactic tides and gravitational interactions.
In fact,
this
bright open cluster, known as M46, is around 300 million years
young.
It still contains a few hundred stars within a span of
30 light-years or so.
Located about 5,000 light-years away toward the
constellation
Puppis, M46
also seems to contain contradictions to its youthful status.
In this pretty starscape,
the colorful, circular patch above and right of the center of M46
is the planetary nebula NGC 2438.
Fainter still, a second planetary nebula, PK231+4.1,
is identified
by the box at the right and enlarged in the inset.
Planetary nebulae are a brief, final phase in the life of a sun-like
star a billion
years old or more,
whose central reservoir of hydrogen fuel has been exhausted.
NGC 2438
is estimated to be only 3,000 light-years distant, though, and
moves at a different speed than M46 cluster members.
Along with its fainter cohort, planetary nebula NGC 2438 is likely
only by chance
appearing near our line-of-sight to the young stars of M46.
APOD: 2015 April 6 - NGC 3293: A Bright Young Star Cluster
Explanation:
Hot blue stars
shine brightly in this beautiful, recently formed galactic or
"open" star cluster.
Open cluster
NGC 3293 is located in the
constellation Carina, lies at a distance of about 8000
light years, and has a particularly high abundance of
these young bright stars.
A study of
NGC 3293
implies that the blue stars are only about 6 million years old, whereas the
cluster's dimmer, redder stars appear to be
about 20 million years old.
If true, star formation in this
open cluster
took at least 15 million years.
Even this amount of time is short, however,
when compared with the billions of years stars like our
Sun live,
and the over-ten billion year lifetimes of many
galaxies and our
universe.
Pictured,
NGC 3293 appears just in front of a dense
dust lane
and red glowing hydrogen gas emanating from the
Carina Nebula.
APOD: 2015 March 7 - NGC 602 in the Flying Lizard Nebula
Explanation:
Near the outskirts of the
Small Magellanic Cloud,
a satellite galaxy some 200 thousand light-years distant,
lies 5 million year
young
star cluster NGC 602.
Surrounded by natal gas and dust,
NGC 602
is just below center in this
telescopic field of view with the angular size of
the Full Moon on the sky.
The cluster itself is about 200 light-years in diameter.
Glowing interior ridges and swept back shapes strongly suggest that
energetic radiation and shock waves from NGC 602's massive
young stars have eroded the dusty material and triggered a
progression
of star formation moving away from the cluster's center.
Of course, the more extended wings of emission in the
region suggest a popular name for
the complex cosmic environment,
The
Flying Lizard Nebula.
APOD: 2015 January 5 - A Fox Fur, a Unicorn, and a Christmas Tree
Explanation:
What do the following things have in common:
a cone, the fur of a fox, and a Christmas tree?
Answer: they all occur in the constellation of the unicorn
(Monoceros).
Pictured as a star forming region
and cataloged as NGC 2264, the complex jumble of
cosmic gas and dust is about 2,700 light-years distant and
mixes reddish emission nebulae
excited by energetic light from
newborn stars with dark
interstellar dust clouds.
Where the otherwise obscuring dust clouds lie close
to the hot, young stars they also reflect starlight, forming blue
reflection nebulae.
The image spans about the diameter of a full moon,
covering about 30
light-years at the distance of NGC 2264.
Its cast of cosmic characters includes
the Fox Fur Nebula, whose
convoluted pelt lies on the lower right, bright
variable star
S Mon visible just above the Fox Fur, and the
Cone Nebula on the image left.
Given their distribution, the stars of NGC 2264 are also known as the
Christmas Tree
star cluster.
The triangular tree shape traced by the stars appears here
with its apex at the
Cone Nebula on the left with its broader base
near S Mon on the right.
APOD: 2014 November 28 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as NGC 281
and you might miss the stars of open cluster
IC 1590.
But, formed
within
the nebula, that cluster's young, massive stars
ultimately power the pervasive
nebular glow.
The eye-catching shapes looming in
this portrait
of NGC 281 are sculpted columns and dense
dust globules
seen in silhouette, eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Playfully called
the Pacman Nebula because of its overall shape,
NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This sharp composite image was made through
narrow-band filters,
combining emission from the nebula's hydrogen, sulfur, and oxygen
atoms in green, red, and blue hues.
It spans over 80 light-years at the estimated distance of NGC 281.
APOD: 2014 October 8 - NGC 6823: Cloud Sculpting Star Cluster
Explanation:
Star cluster NGC 6823 is slowly turning gas clouds into stars.
The center of the open cluster, visible on the upper right,
formed only about two million years ago and is
dominated in brightness by a host of
bright young blue stars.
Some outer parts of the cluster, visible in the
featured image's center
as the stars and pillars of
emission nebula
NGC 6820, contain even younger stars.
The huge pillars of gas and
dust likely get their elongated shape by
erosion from hot radiation emitted from the
brightest cluster stars.
Striking dark globules
of gas and dust are also visible across the upper left of the
featured image.
Open star cluster
NGC 6823 spans
about 50 light years and lies about 6000
light years away toward the
constellation
of the Fox (Vulpecula).
APOD: 2014 September 24 - The Lagoon Nebula in Stars Dust and Gas
Explanation:
The large majestic
Lagoon Nebula
is home for many young stars and hot gas.
Spanning 100 light years across while lying only about 5000 light years distant, the
Lagoon Nebula is so big and bright that
it can be
seen without a
telescope toward the
constellation of
Sagittarius.
Many bright stars are visible from
NGC 6530, an
open cluster that
formed in the nebula only several million years ago.
The greater nebula, also known as
M8 and NGC 6523,
is named "Lagoon" for the band of dust seen to the
left of the open cluster's center.
A bright knot of gas and dust in the
nebula's center is known as the
Hourglass Nebula.
The featured picture is a newly processed panorama of
M8, capturing five times the diameter of the Moon.
Star formation continues in the
Lagoon Nebula as witnessed by the many
globules that exist there.
APOD: 2014 September 3 - M6: The Butterfly Cluster
Explanation:
To some, the outline of the open cluster of stars M6 resembles a butterfly.
M6, also known as NGC 6405,
spans about 20 light-years and lies about
2,000 light years distant.
M6,
pictured above, can best be seen in a dark sky with binoculars
towards the constellation of the Scorpion (Scorpius), coving about as much of the sky as the
full moon.
Like other open clusters, M6 is composed predominantly of
young blue stars,
although the brightest star is nearly orange.
M6 is estimated to be about 100 million years old.
Determining the distance to clusters like
M6
helps astronomers calibrate the distance scale of the universe.
APOD: 2014 August 29 - The Wizard Nebula
Explanation:
Open star cluster NGC 7380 is still embedded in
its natal cloud
of interstellar gas and dust popularly known as the
Wizard Nebula.
Seen with foreground and background stars
along the
plane of our Milky Way galaxy
it lies some 8,000 light-years distant, toward the constellation
Cepheus.
A full moon would easily fit inside this telescopic view of
the 4 million year
young
cluster and associated nebula, normally
much too faint to be seen by eye.
Made with telescope and camera firmly planted on Earth,
the image reveals multi light-year sized shapes and structures
within the Wizard in a color palette made
popular in Hubble Space Telescope images.
Recorded with narrowband filters, the visible wavelength light
from the nebula's hydrogen, oxygen, and sulfur atoms is transformed
into green, blue, and red colors in the final digital composite.
But there is still a
trick
up the Wizard's sleeve.
Sliding your cursor over the image
(or following this
link)
will make the stars disappear, leaving only the cosmic gas and
dust of the Wizard Nebula.
APOD: 2014 August 28 - Messier 20 and 21
Explanation:
The beautiful Trifid Nebula,
also known as Messier 20, is easy
to
find with a small telescope in the nebula rich constellation
Sagittarius.
About 5,000 light-years away, the colorful study in
cosmic contrasts shares
this
well-composed, nearly 1 degree wide field with
open star cluster
Messier 21
(top right).
Trisected by dust lanes
the Trifid itself is about 40 light-years across and
a mere 300,000 years old.
That makes it one of the
youngest star forming
regions in our sky,
with newborn and embryonic stars embedded in its
natal dust and gas clouds.
Estimates of the distance to open star cluster M21 are similar to M20's,
but though they share this gorgeous telescopic skyscape
there is no apparent connection between the two.
In fact, M21's stars are much older, about 8 million
years old.
APOD: 2014 June 8 - Open Cluster NGC 290: A Stellar Jewel Box
Explanation:
Jewels don't shine this bright -- only stars do.
Like gems in a jewel box, though, the stars of
open cluster
NGC 290 glitter in a
beautiful display of brightness and color.
The photogenic cluster,
pictured above, was captured recently by the orbiting
Hubble Space Telescope.
Open clusters of stars are younger, contain few stars,
and contain a much higher fraction of blue stars than do
globular clusters of stars.
NGC 290 lies about 200,000
light-years
distant in a neighboring galaxy called the
Small Cloud of Magellan (SMC).
The open cluster contains hundreds of stars
and spans about 65 light years across.
NGC 290
and other open clusters are good laboratories for studying how
stars of different masses evolve,
since all the open cluster's stars were born at about the same time.
APOD: 2014 April 8 - M42: Inside the Orion Nebula
Explanation:
The Great Nebula in Orion,
an immense, nearby
starbirth region,
is probably the most famous of all
astronomical nebulas.
Here, glowing gas surrounds hot young stars at the edge of an
immense interstellar
molecular cloud only 1500
light-years away.
In the above deep image composite in assigned colors taken by the
Hubble Space Telescope
wisps and sheets of dust and gas are particularly evident.
The Great Nebula in Orion can be found with the
unaided eye near the
easily identifiable
belt of three stars in the popular constellation
Orion.
In addition to housing a bright
open cluster of stars known as the
Trapezium, the
Orion Nebula contains many
stellar nurseries.
These nurseries contain much
hydrogen gas, hot young stars,
proplyds, and
stellar jets
spewing material at high speeds.
Also known as
M42, the
Orion Nebula spans about 40 light years and is located in the same
spiral arm of
our Galaxy as the
Sun.
APOD: 2014 March 11 - In the Heart of the Rosette Nebula
Explanation:
In the heart of the
Rosette Nebula lies a bright
open cluster
of stars that lights up the nebula.
The stars of NGC 2244 formed from the surrounding gas only a few million years ago.
The above image
taken in January using multiple exposures and very specific colors of
Sulfur (shaded red),
Hydrogen (green), and
Oxygen (blue),
captures the central region in tremendous detail.
A hot wind of particles streams away from the cluster stars
and contributes to an already complex menagerie of gas and
dust filaments while slowly evacuating the cluster center.
The Rosette Nebula's
center measures about 50 light-years across, lies about 4,500 light-years away,
and is visible with binoculars towards the constellation of
the Unicorn
(Monoceros).
APOD: 2014 February 25 - The Pleiades Deep and Dusty
Explanation:
The well known
Pleiades
star cluster is slowly destroying part of a passing cloud of
gas and dust.
The Pleiades
is the brightest
open cluster of stars
on Earth's sky and
can be seen from almost any northerly location with the
unaided eye.
The passing young dust cloud is thought to be part of
Gould's belt, an
unusual ring of young star formation surrounding the Sun in the
local Milky Way Galaxy.
Over the past 100,000 years, part of
Gould's belt
is by chance moving right through the older
Pleiades and is causing
a strong reaction between stars and dust.
Pressure from the stars' light significantly repels the dust in the surrounding blue
reflection nebula, with
smaller dust particles being repelled more strongly.
A short-term result is that parts of the dust cloud have become
filamentary and
stratified, as seen in the
above deep-exposure image.
APOD: 2014 February 22 - M44: The Beehive Cluster
Explanation:
A mere 600 light-years away,
M44 is one of the closest
star clusters to our solar system.
Also known as the
Praesepe
or the Beehive cluster its stars
are young though, about 600 million years old compared to our Sun's
4.5 billion years.
Based on similar ages and motion through space, M44 and the
even closer Hyades star cluster in Taurus
are thought to have
been born together in the same large molecular cloud.
An open cluster
spanning some 15 light-years, M44 holds 1,000 stars or so
and covers about 3 full moons (1.5 degrees) on the
sky in the constellation Cancer.
Visible to the unaided eye, M44 has been recognized since antiquity.
Described as a faint cloud or celestial mist long before
being included as the 44th entry in Charles Messier's
18th century catalog, the cluster was not resolved into its individual
stars until telescopes were available.
A popular target for modern, binocular-equiped sky gazers,
the cluster's few
yellowish tinted, cool,
red giants are scattered
through the field of its brighter hot blue main sequence
stars in this colorful
stellar group snapshot.
APOD: 2014 January 23 - Double Cluster in Perseus
Explanation:
This
lovely starfield
spans some seven full moons (about 3.5 degrees) across the
heroic northern constellation of
Perseus.
Just right of center it holds the famous pair of open or galactic
star clusters, h and Chi Persei.
Also cataloged as
NGC
869 (right) and NGC 884,
both clusters are about 7,000 light-years away and
contain stars much younger and hotter than the Sun.
Separated by only a few hundred light-years, the clusters are
both 13 million years young
based on
the ages of
their individual
stars,
evidence that they were likely a product of the same
star-forming region.
Always a rewarding
sight in binoculars,
the Double Cluster is
even visible to the unaided eye from
dark locations.
Not seen in binoculars though, and not often depicted in
telescopic images of the region are faint clouds of reddish ionized
hydrogen gas found throughout this remarkable cosmic skyscape.
A color composite, the image includes narrowband data to
enhance emission from the hydrogen clouds.
Visible toward the upper left of the wide
field of view is
another, smaller open star cluster,
NGC 957,
also of similar age, distance, and possibly related
to the more famous Double Cluster in Perseus.
APOD: 2014 January 7 - M7: Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark
sky
in the tail of the constellation of the Scorpion (Scorpius).
M7 contains about 100 stars in total, is about
200 million years old,
spans 25
light-years across, and lies about 1000 light-years away.
The above deep image, taken last June from
Hungary
through a small telescope, combines over 60 two-minute exposures.
The M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year
130 AD.
Also visible are a
dark dust cloud
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2013 October 26 - NGC 7789: Caroline's Rose
Explanation:
Found among the rich starfields of the Milky Way toward the
constellation Cassiopeia,
star
cluster NGC 7789 lies about 8,000 light-years away.
A late 18th century
deep sky discovery of astronomer
Caroline Lucretia Herschel,
the cluster is also known as Caroline's Rose.
Its suggestive appearance is created by the cluster's nestled
complex of stars and voids.
Now estimated to be 1.6 billion years young, the
galactic or open cluster of stars also shows its age.
All the stars in the cluster were likely born
at the same time, but the brighter and more massive ones have more
rapidly exhausted the hydrogen fuel in their
cores.
These have evolved from
main sequence
stars like the Sun into the many red giant stars shown with a
yellowish cast in this lovely color composite.
Using measured
color and brightness, astronomers
can model the mass and hence the age of
the cluster stars just starting to "turn off" the main sequence
and become red giants.
Over 50 light-years across,
Caroline's Rose spans about
half a degree (the angular size of the moon)
near the center of the wide-field telescopic image.
APOD: 2013 October 8 - The Bubble and M52
Explanation:
To the eye,
this
cosmic composition nicely balances the
Bubble Nebula at the lower left with open star cluster M52 above it and to the right.
The pair would be lopsided on other scales, though.
Embedded in a complex of
interstellar dust
and gas and blown by the winds from a single, massive
O-type star, the
Bubble Nebula, also known as NGC 7635, is a
mere 10 light-years wide.
On the other hand,
M52 is a rich open
cluster of around a thousand stars.
The cluster is about 25 light-years across.
Seen toward the northern boundary
of Cassiopeia, distance estimates
for the Bubble Nebula and associated cloud complex are around
11,000 light-years, while
star cluster M52
lies nearly 5,000 light-years away.
The wide telescopic field of view spans about two degrees on the sky
or four times the apparent size of the Full Moon.
APOD: 2013 September 18 - M45: The Pleiades Star Cluster
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it as dusty as this.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The above exposure took about 20 minutes and covers a sky area several times the size of the full moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye.
The actual number of
Pleiades stars visible, however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2013 August 6 - In the Vicinity of the Cone Nebula
Explanation:
Strange shapes and textures can be found in neighborhood
of the Cone Nebula.
The unusual shapes
originate from fine interstellar
dust reacting in
complex ways with the energetic light and
hot gas being expelled by the young stars.
The brightest star on the right of the
above picture is S Mon,
while the region just below it has been nicknamed the
Fox Fur Nebula for its color and structure.
The blue glow directly surrounding
S Mon results from
reflection,
where neighboring dust reflects light from the bright star.
The red glow
that encompasses the whole region results not only from
dust reflection but also emission from
hydrogen gas ionized by starlight.
S Mon
is part of a young open
cluster of stars named
NGC 2264, located about 2500 light years away toward the constellation of the Unicorn
(Monoceros).
Even though it points right at S Mon, details of the origin of the mysterious geometric Cone Nebula, visible on the far left, remain
a mystery.
APOD: 2013 January 13 - NGC 602 and Beyond
Explanation:
Near the outskirts of the
Small Magellanic Cloud,
a satellite galaxy some 200 thousand light-years distant,
lies 5 million year young
star cluster NGC 602.
Surrounded by natal gas and dust,
NGC 602 is featured in this
stunning Hubble image of the region.
Fantastic ridges and swept
back shapes strongly suggest that
energetic radiation and shock waves from NGC 602's massive
young stars have eroded the dusty material and triggered a
progression
of star formation moving away from the cluster's center.
At the estimated distance of the Small Magellanic Cloud, the
picture spans about 200 light-years, but
a tantalizing assortment of
background galaxies are also visible in the sharp Hubble view.
The background galaxies are hundreds of millions of
light-years or more beyond NGC 602.
APOD: 2013 January 3 - Open Star Clusters M35 and NGC 2158
Explanation:
Open clusters of stars can be near or far, young or old,
and diffuse or compact.
Found near the plane
of our Milky Way galaxy, they
contain from 100 to 10,000 stars, all of which formed at
nearly the same time.
Bright blue stars frequently
distinguish younger open clusters.
M35,
on the upper left, is relatively nearby at 2800
light years distant, relatively young at 150 million years old, and relatively diffuse, with about 2500 stars spread out over a
volume 30 light years across.
An older and more compact open cluster,
NGC 2158,
is at the lower right.
NGC 2158 is four times
more distant than
M35,
over 10 times older, and much more compact with many
more stars in roughly the same volume of space.
NGC 2158's bright blue stars have
self-destructed,
leaving cluster light to be dominated by
older and yellower stars.
Both
clusters are seen toward the constellation of
Gemini.
APOD: 2013 January 1 - A Double Star Cluster
Explanation:
Few star clusters are seen to be so close to each other.
Some 7,000 light-years away, though, this pair of open or galactic
star clusters is an easy
binocular target, a lovely starfield in the
northern constellation
Perseus.
Also visible to
the unaided eye from dark sky areas,
it was cataloged in 130 BC by Greek astronomer Hipparchus.
Now known as
h and
chi Persei, or
NGC 869 (above right) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun.
In addition to being physically close together,
the clusters' ages
based on
their individual stars are similar - evidence that both
clusters were likely a product of the same
star-forming region.
APOD: 2012 December 24 - Hyades for the Holidays
Explanation:
Recognized since antiquity and depicted on the
shield of Achilles according to Homer,
stars of the
Hyades cluster
form the head of the constellation Taurus the Bull.
Their general V-shape is anchored by
Aldebaran,
the eye of the Bull and by far the constellation's brightest star.
Yellowish in appearance, red giant Aldebaran is not a Hyades cluster
member, though.
Modern astronomy puts
the
Hyades cluster 151 light-years away
making it the nearest established open star cluster,
while Aldebaran lies at less than half that distance, along the same
line-of-sight.
Along
with colorful Hyades stars, this stellar holiday portrait
locates Aldebaran just below center, as well as another
open
star cluster in Taurus, NGC 1647 at the left,
some 2,000 light-years or more in the background.
Just slide your cursor over the image to identify the stars.
The central Hyades stars are spread out over about 15 light-years.
Formed some 800 million years ago, the Hyades star cluster may
share a common origin
with M44
(Praesepe), a naked-eye open star cluster in Cancer,
based on M44's
motion through space
and remarkably similar age.
APOD: 2012 September 12 - M7: Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of the Scorpion (Scorpius).
M7 contains about 100 stars in total, is about
200 million years old,
spans 25
light-years across, and lies about 1000 light-years away.
The above deep exposure was taken from
Hakos Farm in
Namibia.
The M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year
130 AD.
Also visible are a
dark dust cloud
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2012 February 15 - Meropes Reflection Nebula
Explanation:
Reflection nebulas reflect light from a nearby star.
Many small carbon
grains in the nebula reflect the light.
The blue color typical of reflection nebula is caused by blue light being
more efficiently scattered by the carbon
dust than red light.
The brightness of
the nebula is determined by the
size and density of the reflecting grains,
and by the color and brightness of the neighboring star(s).
NGC 1435,
pictured above, surrounds
Merope
(23 Tau), one of the brightest stars in the
Pleiades (M45).
The Pleiades nebulosity is caused by a chance encounter between an
open cluster of stars and a dusty
molecular cloud.
APOD: 2011 December 13 - In the Vicinity of the Cone Nebula
Explanation:
Strange shapes and textures can be found in neighborhood
of the Cone Nebula.
The unusual shapes
originate from fine interstellar
dust reacting in
complex ways with the energetic light and
hot gas being expelled by the young stars.
The brightest star on the right of the
above picture is S Mon,
while the region just below it has been nicknamed the
Fox Fur Nebula for its color and structure.
The blue glow directly surrounding
S Mon results from
reflection,
where neighboring dust reflects light from the bright star.
The red glow
that encompasses the whole region results not only from
dust reflection but also emission from
hydrogen gas ionized by starlight.
S Mon
is part of a young open
cluster of stars named
NGC 2264, located about 2500 light years away toward the constellation of the Unicorn
(Monoceros).
The origin of the mysterious geometric Cone Nebula, visible on the far left, remains
a mystery.
APOD: 2011 November 2 - NGC 7380: The Wizard Nebula
Explanation:
What powers are being wielded in the Wizard Nebula?
Gravitation strong enough to form stars, and
stellar winds
and radiations powerful enough to create and dissolve
towers of gas.
Located only 8,000 light years away, the Wizard nebula,
pictured above, surrounds developing open star cluster NGC 7380.
Visually, the interplay of stars, gas, and dust has created a shape that appears to some like a fictional
medieval sorcerer.
The active star forming region spans 100 about light years, making it appear larger than the angular extent of the Moon.
The Wizard Nebula
can be located with a small telescope toward the constellation of the King of Aethiopia
(Cepheus).
Although the
nebula may last only a few million years, some of the stars being formed may outlive our Sun.
APOD: 2011 September 21 - Pleiades Deep Field
Explanation:
Have you ever seen the Pleiades star cluster?
Even if you have, you probably have never seen it like this: all dusty.
Perhaps the most famous star cluster on the sky, the bright stars of the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
With a long exposure from a dark location, though, the dust cloud surrounding the
Pleiades star
cluster becomes very evident.
The above exposure took about 30 hours and covers a sky area several times the size of the full moon.
Also known as the Seven Sisters and
M45,
the Pleiades lies about 400 light years away toward the constellation of the Bull
(Taurus).
A common legend with a
modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye.
The actual number of
Pleiades stars visible, however, may be more or less than seven, depending on the
darkness of the surrounding sky and the
clarity of the observer's eyesight.
APOD: 2011 September 14 - The Bubble and M52
Explanation:
To the eye,
this
cosmic composition nicely balances the
Bubble Nebula at the lower right with open star cluster M52.
The pair would be lopsided on other scales, though.
Embedded in a complex of
interstellar dust
and gas and blown by the winds from a single, massive
O-type star, the
Bubble Nebula, also known as NGC 7635, is a
mere 10 light-years wide.
On the other hand,
M52 is a rich open
cluster of around a thousand stars.
The cluster is about 25 light-years across.
Seen toward the northern boundary
of Cassiopeia, distance estimates
for the Bubble Nebula and associated cloud complex are around
11,000 light-years, while
star cluster M52
lies nearly 5,000 light-years away.
The wide telescopic field of view spans about 1.5 degrees on the sky
or three times the apparent size of the Full Moon.
APOD: 2011 September 6 - M6: The Butterfly Cluster
Explanation:
To some, the outline of the open cluster of stars M6 resembles a butterfly.
M6, also known as NGC 6405,
spans about 20 light-years and lies about
2,000 light years distant.
M6 can best be seen in a dark sky with binoculars
towards the constellation of Scorpius, coving about as much of the sky as the
full moon.
Like other open clusters, M6 is composed predominantly of
young blue stars,
although the brightest star is nearly orange.
M6 is estimated to be about 100 million years old.
Determining the distance to clusters like
M6 helps astronomers calibrate the distance scale of the universe.
APOD: 2011 September 3 - Comet Garradd Passes Ten Thousand Stars
Explanation:
Comet Garradd continues to brighten as it drifts across the northern sky.
Last week the comet, visible with binoculars and discernible by its
green coma,
passed nearly in front of globular cluster M71.
M71 was once thought to be an open cluster, but is now known to be an older
globular cluster
containing over 10,000 stars.
The photogenic duo was captured with a standard digital camera in a 10-minute, wide-angle exposure toward the northern constellation of the Arrow (Sagitta).
The stars
Sham (alpha Sagittae),
beta Sagittae,
gamma Sagittae, and the
double star
delta Sagittae are
all visible in a diagonal band running down from the upper left.
Comet C/2009 P1 (Garradd), will
remain visible in northern skies for months and will reach its closest approach to the Sun in December.
APOD: 2011 August 25 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as
NGC 281
and it's almost easy to miss stars of open cluster
IC 1590.
But, formed
within
the nebula, that cluster's young, massive stars
ultimately power the pervasive
nebular glow.
The eye-catching shapes looming in
this portrait
of NGC 281 are sculpted columns and dense
dust globules seen in silhouette,
eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Playfully called
the Pacman Nebula because of its overall shape,
NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This composite image was made through
narrow-band filters,
but combines emission from the nebula's hydrogen, sulfur, and oxygen atoms
in a visible spectrum palette.
It spans
over 80 light-years at the estimated distance of NGC 281.
APOD: 2011 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of
this flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to
glow.
The Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of
the Unicorn
(Monoceros).
APOD: 2010 December 2 - Hartley 2 Star Cluster Tour
Explanation:
Early in November, small
but active
Comet Hartley 2 (103/P Hartley) became the
fifth comet
imaged close-up by a
spacecraft
from planet Earth.
Continuing its own
tour
of the solar system with a 6 year
orbital period, Hartley 2 is
now appearing in the
nautical
constellation Puppis.
Still a target for binoculars or small telescopes from dark sky
locations, the comet is captured in this composite image
from November 27, sharing the rich 2.5 degree wide
field of view
with some star clusters well known
to earthbound skygazers.
Below and right of the comet's alluring green coma lies
bright M47,
a young open star cluster some 80 milion years old,
about 1,600 light-years away.
Below and left open cluster
M46 is older,
around 300 million years of age, and 5,400 light-years distant.
Hartley 2's short, faint tail even extends
up and right
toward another fainter star cluster in the scene, NGC 2423.
On November 27, Comet Hartley 2 was about 2.25
light-minutes from Earth.
Sweeping toward
the bottom of this field, by November 28 the
comet's path had carried it between M46 and M47.
APOD: 2010 October 26 - Comet Hartley Passes a Double Star Cluster
Explanation:
Most star clusters are singularly impressive.
Open clusters NGC 869 and NGC 884,
however, are doubly impressive.
Also known as "h and chi Persei", this unusual
double cluster, shown above, is bright enough to be seen from a
dark location without even
binoculars.
Although their discovery surely predates
written history, the Greek astronomer
Hipparchus
notably cataloged the
double cluster.
The clusters are over 7,000 light years distant toward the
constellation
of Perseus,
but are separated by only hundreds of light years.
Captured earlier this month, the bright comet
103P/Hartley,
informally called Comet
Hartley 2,
passed well in front but only a few degrees away from the famous double cluster.
Comet Hartley 2, visible on the right,
is now fading but
still discernable to northern observers with binoculars.
No binoculars are needed, of course, if you go right up to the
comet's nucleus, as is the plan for NASA's
EPOXI
spacecraft on November 4.
APOD: 2010 August 17 - NGC 4755: A Jewel Box of Stars
Explanation:
The great variety of star colors in this
open cluster underlies its name:
The Jewel Box.
One of the bright central stars is a
red supergiant,
in contrast to the many blue stars that surround it.
The cluster, also known as
Kappa Crucis contains just over 100 stars,
and is about 10 million years old.
Open clusters are younger,
contain few stars, and contain a much higher fraction of
blue stars than do
globular
clusters.
This
Jewel Box lies about 6,400 light-years away, so the light that we see
today was emitted from the cluster before even the
Great Pyramids in
Egypt were built.
The Jewel Box,
pictured above, spans about 20 light-years,
and can be seen with binoculars towards the southern constellation of the cross
(Crux).
APOD: 2010 February 14 - Field of Rosette
Explanation:
What surrounds the florid Rosette nebula?
To better picture this area of the sky, the
famous flowery
emission nebula
on the far right has been captured recently in a deep and
dramatic wide field image that features several other sky highlights.
Designated NGC 2237, the center of the
Rosette nebula is populated by the bright blue stars of
open cluster NGC 2244, whose
winds
and energetic light are evacuating the nebula's center.
Below the famous flower, a symbol of
Valentine's Day, is a
column of dust and gas that appears like a rose's stem but extends hundreds of light years.
Across the
above image, the bright blue star just left and below the center is called
S Monocerotis.
The star is part of the open cluster
of stars labelled NGC 2264 and known as the
Snowflake cluster.
To the right of S Mon is a dark pointy featured called the
Cone nebula, a nebula likely shaped by winds flowing out a massive star obscured by dust.
To the left of S Mon is the
Fox Fur nebula, a tumultuous region created by the rapidly evolving Snowflake cluster.
The Rosette region, at about 5,000
light years distant, is about twice as far away as the region surrounding S Mon.
The entire field
can be seen with a small telescope toward the
constellation of the
Unicorn
(Monoceros).
APOD: 2010 February 11 - Star Cluster M34
Explanation:
This pretty,
open cluster of stars,
M34, is about the size of
the Full Moon on the sky.
Easy to appreciate in small telescopes,
it lies some 1,800 light-years away in the constellation
Perseus.
At that distance, M34 physically spans about 15 light-years.
Formed at the same time from the same cloud of dust and gas,
all the stars of M34
are about 200 million years young.
But like
any open star cluster orbiting in the
plane of
our galaxy, M34 will eventually disperse as it experiences
gravitational tides and encounters with the
Milky Way's
interstellar clouds and other stars.
Over four billion years ago, our own Sun was likely
formed in a similar
open star cluster.
APOD: 2010 January 13 - The Spider and the Fly
Explanation:
Bright clusters and nebulae abound in the ancient northern
constellation of
Auriga.
The region
includes the open star cluster
M38, emission nebula
IC 410 with
Tadpoles, Auriga's own
Flaming Star Nebula IC 405, and
this interesting pair
IC 417 (lower left) and NGC 1931.
An imaginative eye toward the expansive
IC 417
and diminutive
NGC 1931
suggests a cosmic
spider and fly.
About 10,000 light-years distant,
both represent young, open star clusters formed in interstellar
clouds and still embedded in
glowing hydrogen gas.
For scale, the more compact NGC 1931 is about 10 light-years across.
APOD: 2009 December 4 - The Double Cluster
Explanation:
A
lovely starfield
in the heroic northern constellation
Perseus
holds this famous pair of open or galactic star clusters,
h and Chi
Persei.
Also cataloged as
NGC
869 (right) and NGC 884,
both clusters are about 7,000 light-years away and
contain stars much younger and hotter than the Sun.
Separated by only a few hundred light-years, the clusters' ages
based on
their individual stars
are similar - evidence that they were likely a product of the same
star-forming region.
Always a rewarding
sight in binoculars,
the Double Cluster is
even visible to the unaided eye from
dark locations.
Star colors (and spikes) are enhanced in this beautiful, wide field,
telescopic image.
APOD: 2009 November 8 - M7: Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of the Scorpion (Scorpius).
M7 contains about 100 stars in total, is about
200 million years old,
spans 25
light-years across, and lies about 1000 light-years away.
The above deep exposure was taken last month over several nights from
Yalbraith,
NSW,
Australia.
The M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year
130 AD.
Also visible are a
dark dust cloud
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2009 October 30 - The Bubble and M52
Explanation:
To the eye,
this cosmic composition
nicely balances the
Bubble Nebula at the upper right with open star cluster M52.
The pair would be lopsided on other scales, though.
Embedded in a complex of
interstellar dust
and gas and blown by the winds from a single, massive
O-type star, the
Bubble Nebula (aka NGC 7635) is a
mere 10 light-years wide.
On the other hand,
M52 is a rich open
cluster of around a thousand stars.
The cluster is about 25 light-years across.
Seen toward the northern boundary
of Cassiopeia, distance estimates
for the Bubble Nebula and associated cloud complex are around
11,000 light-years, while
star cluster M52
lies nearly 5,000 light-years away.
APOD: 2009 October 14 - Pleiades and Stardust
Explanation:
Have you ever seen the Pleiades star cluster?
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades is one of the
brightest and closest open clusters.
Hurtling through a cosmic dust cloud a mere 400 light-years away,
the Pleiades
or Seven Sisters
star cluster is well-known for its striking blue
reflection nebulae.
This remarkable wide-field (3 degree)
image of the region
shows the famous
star cluster near the center, while
highlighting lesser known dusty
reflection nebulas
nearby, across an area that would
span
over 20
light-years.
In this case, the sister stars and
cosmic dust clouds
are not related, they just happen to be passing through
the same region of space.
APOD: 2009 October 6 - The Lagoon Nebula from GigaGalaxy Zoom
Explanation:
The large majestic
Lagoon Nebula
is home for many young stars and hot gas.
Spanning 100 light years across while lying only about 5000 light years distant, the
Lagoon Nebulae is so big and bright that
it can be
seen without a
telescope toward the
constellation of
Sagittarius.
Many bright stars are visible from
NGC 6530, an
open cluster that
formed in the nebula only several million years ago.
The greater nebula, also known as
M8 and NGC 6523,
is named "Lagoon" for the band of dust seen to the
left of the open cluster's center.
A bright knot of gas and dust in the
nebula's center is known as the
Hourglass Nebula.
The above picture is a newly released, digitally stitched panorama of
M8 taken as part of the
GigaGalaxy Zoom project
by the
Wide Field
Imager attached to the
MPG/ESO 2.2-meter Telescope at the
La Silla Observatory
in Chile.
The vista spans three times the diameter of the Moon, while the
highest resolution image version occupies over 350 million pixels.
Star formation continues in the
Lagoon Nebula as witnessed by the many
globules that exist there.
APOD: 2009 August 31 - Open Cluster M25
Explanation:
Many stars like our Sun were formed in open clusters.
The
above pictured open cluster,
M25,
contains thousands of stars and is about two thousand
light years distant.
The stars in this cluster all formed together about 90 million years ago.
The bright young stars in
M25
appear blue.
Open clusters,
also called galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike
globular clusters,
open clusters
are generally confined to the
plane of our Galaxy.
M25 is visible with
binoculars towards the
constellation of the Archer
(
Sagittarius).
APOD: 2009 April 12 - M39: Open Cluster in Cygnus
Explanation:
Lying just at the limit of
human perception is a
picturesque starfield containing one of the larger
open clusters on the northern sky.
Spanning an angle larger than the
Moon, M39's relatively few stars
lie only about 800
light years distant toward the constellation of Cygnus.
The above picture of
M39 is a mosaic of 33 images taken by the
WIYN telescope on
Kitt Peak in
Arizona,
USA.
The stars in M39 are all about 300 million years old,
much younger than the 5,000 million years of our
Sun.
Open clusters, also called
galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike globular clusters,
open clusters are generally confined to the
plane of our Galaxy.
APOD: 2009 March 26 - Stars Young and Old
Explanation:
Galactic or open star clusters are relatively young.
These swarms of stars are born near the plane of the Milky Way,
but their numbers steadily dwindle as cluster members are
strewn through the Galaxy by gravitational interactions.
This
bright open cluster, known as M46, is around 300 million years
young and still contains a few hundred stars within its span of
30 light-years or so.
Located about 5,000 light-years away toward the
constellation
Puppis, M46
also seems to contain a contradiction to its youthful status.
In the lovely starscape,
the colorful, circular patch just below the center of M46
(also inset at upper left) is the planetary nebula NGC 2438.
Planetary nebulae are a brief,
final phase in the life of a solar-type star a few
billion
years old whose central reservoir of hydrogen
fuel has been exhausted.
In fact, old
NGC 2438
is estimated to be only 3,000 light-years distant and
moves at a different speed than M46 cluster members.
It likely represents a foreground object,
only by chance appearing
along our line-of-sight to young M46.
APOD: 2008 December 23 - Collinder 399: The Coat Hanger
Explanation:
Is this coat hanger a star cluster or an asterism?
This
cosmic hang-up has been debated over much of last century,
as astronomers wondered whether this binocular-visible object is
really a physically associated
open cluster or a chance projection.
Chance star projections are known as
asterisms, an example of which is the popular
Big Dipper.
Recent precise measurements from different vantage points in the Earth's orbit around the Sun
have uncovered discrepant angular shifts indicating that the
Coat Hanger
is better described as an
asterism.
Known more formally as
Collinder 399,
this bright stellar grouping is wider than the
full moon and lies in the
constellation of the
Fox
(Vulpecula).
On the far right of the image is the
open cluster of stars
NGC 6802.
APOD: 2008 December 10 - Portrait of NGC 281
Explanation:
Look through the cosmic cloud cataloged as
NGC 281
and it's almost easy to miss stars of open cluster
IC 1590.
But, formed within the nebula, that cluster's young, massive stars
ultimately power the pervasive
nebular glow.
The eye-catching shapes looming in
this colorful
portrait of NGC 281
are sculpted columns and dense
dust globules seen in silhouette,
eroded by intense, energetic winds and radiation
from the hot cluster stars.
If they survive long enough,
the dusty structures could also be sites of future star formation.
Sometimes called the Pacman Nebula because
of its overall shape in
wider-field
views, NGC 281 is about 10,000 light-years away in the constellation
Cassiopeia.
This composite image was made through
narrow-band filters
and shows emission from the nebula's hydrogen, sulfur, and oxygen atoms
in green, red, and blue hues.
It spans over 80 light-years at the estimated distance of NGC 281.
APOD: 2008 October 26 - Massive Stars in Open Cluster Pismis 24
Explanation:
How massive can a normal star be?
Estimates made from distance, brightness and standard
solar models had given one star in the
open cluster Pismis 24
over 200 times the mass of our Sun, making it a record holder.
This star is the brightest object located just above the gas front in the
above image.
Close inspection of images taken recently with the
Hubble Space Telescope,
however, have shown that Pismis 24-1 derives its
brilliant luminosity
not from a single star but from
three at least.
Component stars would still remain near 100 solar masses,
making them among the more
massive stars currently on record.
Toward the bottom of the image, stars are still forming in the associated
emission nebula
NGC 6357, including several that appear to be
breaking out and illuminating a
spectacular cocoon.
APOD: 2008 August 3 - Open Cluster NGC 290: A Stellar Jewel Box
Explanation:
Jewels don't shine this bright -- only stars do.
Like gems in a jewel box, though, the stars of
open cluster
NGC 290 glitter in a
beautiful display of brightness and color.
The photogenic cluster,
pictured above, was captured recently by the orbiting
Hubble Space Telescope.
Open clusters of stars are younger, contain few stars,
and contain a much higher fraction of blue stars than do
globular clusters of stars.
NGC 290 lies about 200,000
light-years
distant in a neighboring galaxy called the
Small Cloud of Magellan (SMC).
The open cluster contains hundreds of stars
and spans about 65 light years across.
NGC 290 and other open clusters are good laboratories for studying how
stars of different masses evolve,
since all the open cluster's stars were born at about the same time.
APOD: 2007 December 9 - The Fairy of Eagle Nebula
Explanation:
The dust sculptures of the Eagle Nebula are evaporating.
As powerful starlight whittles away these
cool cosmic mountains, the
statuesque pillars that remain
might be imagined as mythical beasts.
Pictured above is one of several striking
dust pillars of the
Eagle Nebula
that might be described as a gigantic alien
fairy.
This fairy, however, is ten
light years tall and spews radiation much hotter than
common fire.
The greater Eagle Nebula, M16,
is actually a giant evaporating shell of gas and
dust inside of which is a growing
cavity filled with a spectacular stellar nursery currently forming an
open cluster of stars.
The above image in scientifically re-assigned colors was
released
as part of the
fifteenth anniversary celebration of the
launch of the
Hubble Space Telescope.
APOD: 2007 November 22 - Pleiades and Stardust
Explanation:
Hurtling through a cosmic dust cloud a mere 400 light-years away,
the lovely Pleiades
or Seven Sisters star cluster is well-known for its striking blue
reflection nebulae.
This remarkable wide-field (3 degree)
image of the region
shows the famous star cluster at the right, while
highlighting lesser known
dusty reflection nebulae nearby, across an area
that would span over 20 light-years.
In this case, the sister stars and
cosmic dust clouds
are not related, they just happen to be passing through
the same region of space.
But astronomers using infrared detectors
have recently found a
dusty disk that really does belong to one young
Pleiades star -- HD 23514.
Surrounding HD 23514, the disk is estimated to be comparable in
size to the terrestrial planet zone in our own
solar system
and likely represents the
debris from the process
of rocky planet formation.
APOD: 2007 November 18 - M45: The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades is one of the
brightest and closest open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the above photograph
are the blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
APOD: 2007 September 13 - NGC 7129 and NGC 7142
Explanation:
This alluring
telescopic image looks toward the constellation
Cepheus
and an intriguing visual pairing of dusty
reflection nebula
NGC 7129 (left) and
open star cluster
NGC 7142.
The two appear separated by only half a degree on the sky,
but they actually lie at quite different distances.
In the foreground,
dusty nebula NGC 7129
is about 3,000 light-years distant, while open cluster
NGC 7142 is likely over
6,000 light-years away.
In fact, the pervasive and clumpy foreground dust clouds in
this region redden the light from NGC 7142,
complicating astronomical
studies of the cluster.
Still, NGC 7142 is thought to be an
older open star cluster, while
the bright stars embedded in NGC 7129 are perhaps a million
years young.
The telltale reddish crescent shapes around NGC 7129 are associated with
energetic jets streaming away from newborn stars.
Surprisingly, despite the dust, far off
background galaxies can be
seen in the colorful cosmic vista.
APOD: 2007 August 9 - Star Cluster Messier 67
Explanation:
Gathered
at the center of this sharp skyview are the stars of
Messier 67,
one of the oldest known
open star clusters.
In fact, though open star clusters are usually much younger, the
stars of M67
are likely around 4 billion years old, about
the same age and with about the same elemental abundances as
the Sun.
Open clusters are almost always
younger because they are dispersed
over time as they encounter other stars,
interstellar clouds, and experience gravitational tides while
orbiting
the center of our galaxy.
Still, M67 contains over 500 stars or so and lies some
2,800 light-years away in the
constellation
Cancer.
At that estimated distance, M67 would be about 12 light-years across.
APOD: 2007 May 9 - The Snowflake Cluster versus the Cone Nebula
Explanation:
Strange shapes and textures can be found in the neighborhood of the Cone Nebula.
These patterns result from the tumultuous unrest that accompanies the formation of the
open cluster of stars known as
NGC 2264, the
Snowflake cluster.
To better understand this process,
a detailed image of this region was taken in two colors of infrared light by the orbiting
Spitzer
Space Telescope.
Bright stars from the
Snowflake cluster dot the field.
These stars soon heat up and destroy the gas and
dust mountains in which they formed.
One such dust mountain is the famous Cone Nebula, visible in the
above image on the left, pointing toward a bright star near the center of the field.
The entire
NGC 2264 region is located about 2,500
light years away toward the constellation of the
Unicorn
(Monoceros).
APOD: 2007 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of the
this flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to glow.
The
Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of Monoceros.
APOD: 2007 January 12 - Collinder 399: The Coat Hanger
Explanation:
Is this coat hanger a star cluster or an asterism?
This
cosmic hang-up has been debated over much of last century,
as astronomers wondered whether this binocular-visible object is
really a physically associated
open cluster or a chance projection.
Chance star projections are known as
asterisms, an example of which is the popular
Big Dipper.
Recent precise measurements from different vantage points in the Earth's orbit around the Sun
have recently uncovered discrepant angular shifts indicating that the Coat Hanger is better described as an asterism.
Known more formally as
Collinder 399,
this bright stellar grouping can be seen spanning more than a
full moon toward the direction of the
constellation of the
Fox (Vulpecula).
On the far right of the
above image is the open cluster of stars NGC 6802.
APOD: 2006 December 20 - Star Forming Region NGC 6357
Explanation:
For reasons unknown, NGC 6357 is forming some of the most massive stars ever discovered.
Near the more obvious
Cat's Paw nebula, NGC 6357 houses the open star cluster
Pismis 24, home to these tremendously bright and blue stars.
The overall red glow near the inner star forming region results from the
emission of
ionized
hydrogen gas.
The surrounding nebula,
shown above, holds a complex tapestry of gas,
dark dust, stars still forming, and newly born stars.
The intricate patterns are caused by complex interactions between
interstellar winds,
radiation pressures,
magnetic fields, and
gravity.
NGC 6357 spans about 400 light years and lies about 8,000
light years away toward the constellation of the
Scorpion.
APOD: 2006 December 19 - Massive Stars in Open Cluster Pismis 24
Explanation:
How massive can a normal star be?
Estimates made from distance, brightness and standard
solar models had given one star in the
open cluster Pismis 24
over 200 times the mass of our Sun, making it a record holder.
This star is the brightest object located just to the right of the gas front in the
above image.
Close inspection of images taken recently with the
Hubble Space Telescope,
however, have shown that Pismis 24-1 derives its
brilliant luminosity
not from a single star but from
three at least.
Component stars would still remain near 100 solar masses,
making them among the more
massive stars currently on record.
Toward the image left, stars are still forming in the associated
emission nebula
NGC 6357, including several that appear to be
breaking out and illuminating a
spectacular cocoon.
APOD: 2006 October 27 - The Spider and The Fly
Explanation:
Star clusters and nebulae abound in the
ancient northern constellation
Auriga -
a region that includes the
interesting pair NGC 1931 (lower left) and IC 417.
In this gorgeous
color image, an imaginative eye toward
the expansive
IC 417
and diminutive
NGC 1931
suggests a cosmic
spider
and fly.
About 10,000 light-years distant,
both are young open star clusters formed in interstellar
clouds and still embedded in
glowing hydrogen gas.
The more compact NGC 1931 is about 10 light-years across with
contrasting blue hues characteristic of dust
reflected starlight.
APOD: 2006 October 21 - Tombaugh 4
Explanation:
Clyde Tombaugh discovered
planet Pluto in 1930
while surveying the skies with the 13-inch Lawrence Lowell Telescope.
But the skilled and careful astronomer also went on to discover
star clusters, comets, asteroids, and clusters of galaxies.
For example, pictured is galactic or
open star cluster
Tombaugh 4 in the northern constellation
Cassiopeia.
Published in 1941, Tombaugh's
description, based
on his photographic images from the Lowell 13-inch, indicates the
cluster is small and faint, and comprised of about 30 stars.
Using the apparent brightness of the cluster stars
he estimated the distance to be 20 to 30 thousand
light-years, making Tombaugh 4 over 10 light-years in diameter.
This deep
color image, made with a modern ccd camera
and another 13-inch telescope, includes the region's
foreground stars and faint nebulosities.
APOD: 2006 June 1 - Reflections on NGC 6188
Explanation:
NGC 6188 is an interstellar carnival of
young blue stars,
hot red gas, and
cool dark dust.
Located 4,000 light years away in the
disk of our Galaxy,
NGC 6188 is home to the
Ara OB1 association, a group of bright young stars
whose nucleus forms the open cluster
NGC 6193.
These stars are so bright that some of their blue light reflects off of
interstellar dust
forming the diffuse blue glow surrounding the stars in the
above photograph.
Open cluster NGC 6193 formed about
three million years ago from the surrounding gas,
and appears unusually rich in close binary stars.
The red glow visible throughout the photograph arises from
hydrogen gas heated by the bright stars in Ara OB1.
The dark dust that blocks much of NGC 6188's light was likely formed in the
outer atmospheres of
cooler stars and in
supernovae ejecta.
APOD: 2006 May 1 - Open Cluster NGC 290: A Stellar Jewel Box
Explanation:
Jewels don't shine this bright -- only stars do.
Like gems in a jewel box, though, the stars of
open cluster
NGC 290 glitter in a
beautiful display of brightness and color.
The photogenic cluster,
pictured above, was captured recently by the orbiting
Hubble Space Telescope.
Open clusters of stars are younger, contain few stars,
and contain a much higher fraction of blue stars than do
globular clusters of stars.
NGC 290 lies about 200,000
light-years
distant in a neighboring galaxy called the
Small Cloud of Magellan (SMC).
The open cluster contains hundreds of stars
and spans about 65 light years across.
NGC 290 and other open clusters are good laboratories for studying how
stars of different masses evolve,
since all the open cluster's stars were born at about the same time.
APOD: 2006 February 26 - Inside the Eagle Nebula
Explanation:
From afar, the whole thing looks like an
Eagle.
A closer look at the
Eagle Nebula, however, shows the
bright region is actually a window into the
center of a larger dark shell of
dust.
Through this window, a brightly-lit workshop
appears where a whole
open cluster
of stars is being formed.
In this cavity
tall pillars and
round globules of dark dust and cold
molecular gas
remain where stars are still forming.
Already visible are several young
bright blue stars
whose light and winds are burning away and pushing back the
remaining filaments
and walls of gas and dust.
The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with
binoculars toward the constellation of Serpens.
The above picture combines three specific emitted colors
and was taken with the
0.9-meter telescope on
Kitt Peak,
Arizona,
USA.
APOD: 2006 January 28 - Saturn in the Hive
Explanation:
If you can
find Saturn in tonight's sky, then
you can also find M44,
popularly known as the Beehive
star cluster.
In fact, with a pair of binoculars most casual skygazers should
find it fairly easy to zero in on this
celestial scene.
Saturn is at
opposition - opposite the Sun
in Earth's sky - so, the bright planet rises in the east at sunset
and is visible throughout the night.
Near the
stationary part of its wandering path through
the heavens, Saturn will obligingly linger for a while
in the vicinity of M44 in the relatively faint
constellation Cancer.
Seen here in a photograph from January 25, Saturn (lower right)
is strongly overexposed with the stars of M44 swarming above
and to the left.
The picture approximately corresponds to
the view when looking
through a typical pair of binoculars.
Saturn is
about 64 light-minutes from our fair planet
while M44, one of the closest star clusters, is around
600 light-years away.
APOD: 2006 January 9 - M45: The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above
photograph are the blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes are caused by the telescope itself and may be either distracting or provide aesthetic enhancement, depending on your point of view.)
APOD: 2005 November 18 - The 37 Cluster
Explanation:
For the mostly harmless denizens of planet Earth, the
brighter stars of open cluster
NGC 2169
seem to form a cosmic 37.
(Did you
expect 42?.)
Of course, the improbable numerical
asterism
appears solely by chance and lies at an estimated distance of 3,600
light-years toward the
constellation Orion.
As far as galactic or open star clusters go,
NGC 2169
is a small one, spanning about 7 light-years.
Formed at the same time from the same cloud of dust and gas,
the stars of
NGC 2169 are only about 8 million years old.
Such clusters
are expected to disperse over time as they
encounter other stars, interstellar clouds, and
experience gravitational tides while traveling through
the galaxy.
Over four billion years ago, our own Sun was likely formed
in a similar open
cluster of stars.
APOD: 2005 October 11 - NGC 869 and NGC 884: A Double Open Cluster
Explanation:
Most star clusters are singularly impressive.
Open clusters NGC 869 and NGC 884,
however, are doubly impressive.
Also known as "h and chi Persei", this unusual
double cluster, shown above, is bright enough to be seen from a
dark location without even
binoculars.
Although their discovery surely predates
written history, the Greek astronomer
Hipparchus notably cataloged the "double
cluster".
The clusters are over 7,000 light years distant toward the
constellation of
Perseus, but are separated by only hundreds of light years.
APOD: 2005 September 27 - The Star Pillars of Sharpless 171
Explanation:
Towering pillars of cold gas and dark dust adorn the
center star forming region of Sharpless 171.
An open cluster
of stars is forming there from the gas in cold
molecular clouds.
As energetic light emitted by young massive stars boils away the opaque
dust, the region fragments and
picturesque pillars
of the remnant gas and dust form and slowly evaporate.
The energetic light also illuminates the surrounding
hydrogen gas,
energize it to glow as a red
emission nebula.
Pictured above is the active central region of the
Sharpless 171 greater emission nebula.
Sharpless 171 incorporates
NGC 7822 and the active region Cederblad 214, much of which is
imaged above.
The area above spans about 20
light years, lies about 3,000 light years away,
and can be seen with a telescope toward the northern
constellation of the King of Ethiopia
(Cepheus).
APOD: 2005 August 23 - NGC 281: The Pacman Nebula
Explanation:
NGC 281 is a busy workshop of star formation.
Prominent features include a small
open cluster of stars,
a diffuse red-glowing
emission nebula, large lanes of obscuring
gas and
dust, and dense knots
of dust and gas in which stars may still be forming.
The open cluster
of stars IC 1590 visible around the center
has formed only in the last few million years.
The brightest member of this cluster is actually a
multiple-star system
shining light that helps ionize the nebula's gas,
causing the red glow visible throughout.
The lanes of dust
visible left of center are likely homes
of future star formation.
Particularly striking in the
above photograph are the dark
Bok globules
visible against the bright nebula.
The NGC 281 system, dubbed the
Pacman nebula for its
overall shape, lies about 10 thousand light years distant.
APOD: 2005 August 4 - Stars Young and Old
Explanation:
Galactic or
open star
clusters are relatively young
swarms of bright stars
born
together near the plane of our Milky Way Galaxy.
Separated by about a degree on the sky, two
nice
examples are M46
(upper left) 5,400 light-years in the distance
and M47
(lower right) only 1,600 light-years away toward
the nautical constellation
Puppis.
Around 300 million years
young M46
contains a few hundred stars in a region about 30 light-years
across.
Aged 80 million years,
M47 is a
smaller but looser cluster
of about 50 stars spanning 10 light-years.
But
this
portrait of stellar youth also contains
an ancient interloper.
The small, colorful patch of glowing gas in M46 is actually
the planetary nebula NGC 2438 - the
final phase in the life of a sun-like star billions
of years old.
NGC
2438 is estimated to be only 3,000 light-years distant
and likely represents a foreground object, only by chance appearing
along our line of sight to youthful M46.
APOD: 2005 July 10 - In the Center of the Trapezium
Explanation:
Start with the constellation of Orion.
Near Orion's belt is a fuzzy area known as the
Great Nebula of Orion or
M42.
In this nebula is a bright
star cluster known as the
Trapezium, shown above.
New stellar systems are forming there in gigantic globs of gas and
dust known as Proplyds.
Looking closely at the
above picture also reveals
that gas and dust surrounding some of the
dimmer stars
appears to form structures that point away from the
brighter stars.
The above false color image was made by combining
several exposures from the orbiting
Hubble Space
Telescope.
APOD: 2005 May 9 - Stars, Dust and Nebula in NGC 6559
Explanation:
When stars form, pandemonium reigns.
A textbook
case is the star forming region
NGC 6559.
Visible above are red glowing
emission nebulas of
hydrogen, blue
reflection nebulas of
dust, dark
absorption nebulas of dust, and the stars that formed from them.
The first massive stars formed from the dense gas will emit
energetic light and
winds
that erode, fragment, and
sculpt their birthplace.
And then they
explode.
The resulting morass
can be as beautiful as it is complex.
After tens of millions of years, the dust boils away,
the gas gets swept away, and all that is left is a naked
open cluster of stars.
APOD: 2005 April 6 - The M7 Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of
Scorpius.
M7 contains about 100 stars in total,
is about 200 million years old, spans 25
light-years across, and lies about 1000 light-years away.
This color picture was taken recently at the
Kitt Peak
National Observatory in
Arizona,
USA as part of the
Advanced Observers Program.
The M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year 130 AD.
Also visible is a
dark dust cloud
near the bottom of the frame,
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2005 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland New General Catalog
designation of NGC 2237 doesn't appear to diminish the appearance of the
this flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to glow.
The
Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of Monoceros.
APOD: 2005 January 3 - The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above photograph are the
blue reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes are caused by the telescope itself and may be either distracting or provide aesthetic enhancement, depending on your point of view.)
APOD: 2004 October 20 - NGC 281: Cluster, Clouds, and Globules
Explanation:
NGC 281 is a busy workshop of star formation.
Prominent features include a small
open cluster of stars,
a diffuse red-glowing
emission nebula, large lanes of obscuring
gas and
dust, and dense knots
of dust and gas in which stars may still be forming.
The open cluster
of stars IC 1590 visible around the center
has formed only in the last few million years.
The brightest member of this cluster is actually a
multiple-star system
shining light that helps ionize the nebula's gas,
causing the red glow visible throughout.
The lanes of dust
visible left of center are likely homes
of future star formation.
Particularly striking in the
above photograph are the dark
Bok globules
visible against the bright nebula.
The entire
NGC 281 system lies about 10 thousand light years distant.
APOD: 2004 October 4 - NGC 6823: Cloud Sculpting Star Cluster
Explanation:
Star cluster NGC 6823 is ready for its close-up.
The center of the open cluster,
visible on the upper right,
formed only about two million years ago and is
dominated in brightness by a host of
bright young blue stars.
Outer parts of the cluster,
visible above in the image center
as the stars and pillars of
emission nebula
NGC 6820, contain even younger stars.
The huge pillars of gas and
dust likely get their elongated shape by
erosion from hot radiation emitted from the
brightest cluster stars.
Striking dark globules
of gas and dust are also visible across the bottom of this image by the
25 year old
Canada France Hawaii Telescope.
Open star cluster
NGC 6823 spans
about 50 light years and lies about 6000
light years away toward the
constellation of Vulpecula (The Fox).
APOD: 2004 September 21 - M24: A Sagittarius Starscape
Explanation:
Many vast
star fields in the
plane of our
Milky Way Galaxy are rich in clouds of
dust, and gas.
First and foremost, visible in the
above picture are millions of stars,
many of which are similar to our
Sun.
Next huge filaments of
dark interstellar dust
run across the image and block the light from millions
of more stars yet further across
our Galaxy.
The bright red region on the left is part of the
Omega Nebula, an
emission nebula of mostly hot
hydrogen gas also known as
M17.
A small bright grouping of stars near the image center is the
open cluster
M18, while the long bright streak of stars just right of center is
M24.
On the far right of the image is the picturesque red
emission nebula IC 1283 flanked by two blue
reflection nebulas
NGC 6589 and
NGC 6590.
These objects are visible with a small
telescope toward the constellation of
Sagittarius.
APOD: 2004 June 17 - Comet NEAT and the Beehive Cluster
Explanation:
To the unaided eye, they appeared as similar fuzzy patches.
But when a bright comet passed in front of a bright
star cluster last month,
binoculars and cameras were able to show off their marked differences in dramatic fashion.
Pictured above, the bright comet, C/2001 Q4 (NEAT) shows many details of its coma and tail, while far in the distance the Beehive open cluster,
M44,
shows many of its stars.
Comet Q4 has now faded to the edge of unaided visibility and can best be found with a
sky map
and binoculars from the Northern Hemisphere well into June.
Star cluster
M44
will remain an impressive star cluster toward the constellation of Cancer indefinitely.
APOD: 2004 March 31 - M39: Open Cluster in Cygnus
Explanation:
Lying just at the limit of human perception is a
picturesque starfield containing one of the larger
open clusters on the northern sky.
Spanning an angle larger than the
Moon, M39's relatively few stars
lie only about 800
light years distant toward the constellation of Cygnus.
The above picture of
M39 is a mosaic of 33 images taken by the
WIYN telescope on
Kitt Peak in
Arizona,
USA.
The stars in M39 are all about 300 million years old,
much younger than the 5000 million years of our
Sun.
Open clusters, also called
galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike globular clusters,
open clusters are generally confined to the
plane of our Galaxy.
APOD: 2004 February 22 - The M7 Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of
Scorpius.
M7 contains about 100 stars in total,
is about 200 million years old, spans 25
light-years across, and lies about 1000 light-years away.
This color picture was taken in 1995 at the
Burrell-Schmidt Telescope at
Kitt Peak National Observatory in
Arizona.
The
M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year 130 AD.
Also visible is a
dark dust cloud
near the bottom of the frame,
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2003 December 27 - The Pleiades Star Cluster
Explanation:
Perhaps the most famous star cluster on the sky, the
Pleiades
can be seen without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above
photograph are the blue
reflection nebulae
that surround the brighter cluster
stars.
Low mass, faint, brown dwarfs have also
been found in
the
Pleiades.
(Editors' note: The prominent
diffraction spikes were added
to the image for aesthetic reasons, produced by kite string donated
by Rob Gendler's kids and placed over the telescope dew shield.)
APOD: 2003 December 15 - Open Star Clusters M35 and NGC 2158
Explanation:
Open clusters of stars can be near or far, young or old,
and diffuse or compact.
Open clusters
may contain from 100 to 10,000 stars, all of which formed at
nearly the same time.
Bright blue stars frequently
distinguish younger open clusters.
M35,
pictured above on the upper left, is relatively nearby at 2800 light years distant, relatively young at 150 million years old,
and relatively diffuse, with about 2500 stars spread out over a
volume 30 light years across.
An older and more compact open cluster,
NGC 2158, is
visible above on the lower right.
NGC 2158 is four times more distant that
M35, over 10 times older, and much more compact as it contains many
more stars in roughly the same volume of space.
NGC 2158's bright blue stars have
self-destructed,
leaving cluster light to be dominated by
older and yellower stars.
Both clusters are visible toward the constellation of Gemini -- M35 with binoculars and NGC 2158 with a small telescope.
APOD: 2003 December 2 - NGC 869 and NGC 884: A Double Open Cluster
Explanation:
Most star clusters are singularly impressive.
Open clusters NGC 869 and NGC 884,
however, are doubly impressive.
Also known as "h and chi Persei", this unusual
double cluster, shown above, is bright enough to be seen from a
dark location without even binoculars.
Although their discovery surely predates
written history, the Greek astronomer
Hipparchus notably cataloged the "double
cluster".
The clusters are over 7000 light years distant toward the
constellation of
Perseus, but are separated by only hundreds of light years.
APOD: 2003 September 8 - Stars and Dust of the Lagoon Nebula
Explanation:
The large majestic
Lagoon Nebula
is home for many young stars and hot gas.
Spanning 100 light years across while lying only about 5000 light years distant, the
Lagoon Nebulae is so big and bright that
it can be
seen without a
telescope toward the
constellation of
Sagittarius.
Many bright stars are visible from
NGC 6530, an
open cluster that
formed in the nebula only several million years ago.
The greater nebula, also known as
M8 and NGC 6523,
is named "Lagoon" for the band of dust seen to the
left of the open cluster's center.
A bright knot of gas and dust in the nebula's center is known as the
Hourglass Nebula.
The above picture is a digitally sharpened
composite of exposures taken in specific colors of light emitted by
sulfur (red),
hydrogen (green), and
oxygen (blue).
Star formation continues in the
Lagoon Nebula as witnessed by the many
globules that exist there.
APOD: 2003 April 29 - In the Center of the Rosette Nebula
Explanation:
In the heart of the
Rosette Nebula lies a bright
open cluster
of stars that lights up the nebula.
The stars of NGC 2244 formed from the surrounding gas only a few million years ago.
This just-released image taken by the
CFHT's new
MegaPrime camera shows the region in unprecedented detail.
Although the emission nebula is dominated by red
hydrogen light, the
above image has exaggerated the effect of
green light emitted primarily by small amounts of
oxygen.
A hot wind of particles streams away from the cluster stars
and contributes to an already complex menagerie of gas and
dust filaments while slowly evacuating the cluster center.
The Rosette Nebula's
center measures about 50 light-years across, lies about 4500 light-years away,
and is visible with binoculars towards the constellation of
Monoceros.
APOD: 2003 April 7 - NGC 281: Cluster, Clouds, and Globules
Explanation:
NGC 281 is a busy workshop of star formation.
Prominent features include a small
open cluster of stars,
a diffuse red-glowing
emission nebula, large lanes of obscuring
gas and
dust, and dense knots
of dust and gas in which stars may still be forming.
The open cluster
of stars IC 1590 visible around the center
has formed only in the last few million years.
The brightest member of this cluster is actually a
multiple-star system
shining light that helps ionize the nebula's gas,
causing the red glow visible throughout.
The lanes of dust
visible below the center are likely homes
of future star formation.
Particularly striking in the
above photograph are the dark
Bok globules
visible against the bright nebula.
Stars are surely forming there right now.
The entire
NGC 281 system lies about 10 thousand light years distant.
APOD: 2003 April 3 - Jupiter in the Hive
Explanation:
If you can find planet Jupiter in tonight's sky, then
you can also find M44,
popularly known as the Beehive
star cluster.
In fact, with a pair of binoculars most casual skygazers should
find it easy to zero in on this
celestial scene.
It should be easy because after sunset Jupiter presently
rules the night
as the brightest "star" overhead.
Now near the
stationary part of its wandering path through
the heavens, Jupiter will obligingly linger for a while at a spot
only a degree or so southeast of M44 in the relatively faint
constellation Cancer.
Seen here in a photograph from March 28, Jupiter (lower left)
is strongly overexposed with the stars of M44 swarming above
and to the right.
The picture approximately corresponds to
the view when looking
through a typical pair of binoculars.
Jupiter is
about 30 light-minutes from our fair planet
while M44, one of the closest star clusters, is around
600 light-years away.
APOD: 2003 February 13 - The Eagle Nebula from CFHT
Explanation:
Bright blue stars are still forming in the
dark pillars of the
Eagle Nebula.
Made famous by a
picture from the
Hubble Space Telescope in 1995, the
Eagle Nebula shows the dramatic process of star formation.
To the upper right of the nebula in the
above picture lies the heart of the
open cluster M16.
The bright blue stars of
M16 have been continually forming over the past 5 million years,
most recently in the famous central
gas and
dust pillars known as
elephant trunks.
Light takes about 7000 years to reach us from
M16, which spans about 20
light years and
can be seen
with binoculars toward the constellation of
Serpens.
APOD: 2003 January 22 - M11: The Wild Duck Cluster
Explanation:
Many
stars like our
Sun were formed in
open clusters.
The above pictured open cluster,
M11, contains thousands of stars and is just over
five thousand
light years distant.
The stars in this cluster all formed
together about 250 million years ago.
The bright young stars in
M11 appear blue.
Open clusters, also
called galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike
globular clusters,
open clusters are generally confined to the plane of
our Galaxy.
M11 is visible with binoculars towards the constellation of Scutum.
APOD: 2003 January 7 - Open Star Cluster M38
Explanation:
Open cluster M38
can be seen with binoculars toward the
constellation of Auriga.
M38 is considered an intermediately
rich open cluster
of stars, each of which is about 200 million years old.
Located in the disk of our Milky Way galaxy,
M38
is still young enough to house many bright blue stars,
although it's brightest star is a yellow
giant
shining 900 times brighter than our
Sun.
The cluster spans roughly 25
light-years and lies
about 4000 light-years away.
M38, pictured above, is found only about
2.5 degrees northwest of open cluster
M36.
Loosely bound by gravity,
open clusters
spread out over time as they
orbit the galactic center and their member stars slowly escape.
APOD: 2002 December 1 - The Pleiades Star Cluster
Explanation:
It is the most famous star cluster on the sky. The
Pleiades can be seen
without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The
Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above photograph are the blue
reflection nebulae
that surround the bright cluster
stars.
Low mass, faint,
brown dwarfs have
recently been found in the
Pleiades.
APOD: 2002 November 29 - Open Star Clusters M35 and NGC 2158
Explanation:
Open clusters of stars can be near or far, young or old,
and diffuse or compact.
Open clusters
may contain from 100 to 10,000 stars, all of which formed at
nearly the same time.
Bright blue stars frequently
distinguish younger open clusters.
M35,
pictured above on the upper left, is a relatively nearby at 2800
light years distant, relatively young at 150 million years old,
and relatively diffuse, with about 2500 stars spread out over a
volume 30 light years across.
An older and more compact open cluster,
NGC 2158, is
visible above
on the lower right.
NGC 2158 is four times more distant that
M35, over 10 times older, and much more compact as it contains many
more stars in roughly the same volume of space.
NGC 2158's bright blue stars have
self-destructed,
leaving cluster light to be dominated by
older and yellower stars.
Both clusters are visible toward the
constellation of
Gemini -- M35 with binoculars and NGC 2158 with a small telescope.
APOD: 2002 October 6 - The Lagoon Nebula in Three Colors
Explanation:
The bright
Lagoon Nebula is home to a diverse array of astronomical objects.
Particularly interesting sources include a bright
open cluster of stars and
several energetic
star-forming regions.
When viewed by eye,
cluster light
is dominated by an overall red glow that is caused by
luminous hydrogen gas,
while the dark filaments are caused by absorption by dense
lanes of
dust.
The
above picture,
from the
Curtis-Schmidt Telescope,
however, shows the nebula's emission in three exact colors
specifically emitted by
hydrogen,
oxygen, and
sulfur.
The Lagoon Nebula,
also known as M8 and
NGC 6523, lies about 5000 light-years away.
The Lagoon Nebula can be located
with binoculars in the constellation of
Sagittarius spanning a region
over three times the diameter of a
full Moon.
APOD: 2002 July 22 - Open Cluster NGC 6520 from CFHT
Explanation:
Did you ever have a day when it felt like
a dark cloud
was following you around?
For the open cluster of stars NGC 6520,
every day is like this.
On the left of the
above picture are many of
NGC 6520's bright blue stars.
They formed only millions of years ago - much more
recently than our ancient Sun which formed billions of years ago.
On the right is an
absorption nebula,
molecular cloud
Barnard 86, from which the stars
of NGC 6520 surely formed.
This nebula contains much opaque
dust that blocks
light from the many stars that
would have been visible in the background.
Surrounding
NGC 6520 is part of the tremendously dense starscape in the
bulge of our Milky Way Galaxy,
the extended halo of stars that surrounds the
center of our Galaxy.
NGC 6520 spans about 10
light years and lies about
5500 light years away toward the direction of
Sagittarius.
APOD: 2002 July 17 - Star-Forming Region RCW38 from 2MASS
Explanation:
The star cluster in RCW38 was hiding.
Looking at the
star forming region
RCW38 will not normally reveal
most of the stars in this cluster.
The reason is that the
open cluster
is so young that it is still shrouded in thick
dust that absorbs visible light.
This dust typically accompanies
the gas that condenses to form young stars.
When viewed in
infrared light, however, many stars in RCW38 are
revealed, because dust is less effective at
absorbing infrared light.
The above representative-color image mosaic of RCW38 taken by the
2MASS sky survey in infrared light shows not only many
bright blue stars from the star cluster but clouds of
brightly emitting gas
and dramatic lanes of dark dust.
RCW38 spans about 10 light-years and is located about 5500
light years away towards the constellation of
Vela.
APOD: 2002 May 5 - The M7 Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of
Scorpius.
M7 contains about 100 stars in total,
is about 200 million years old, spans 25
light-years across, and lies about 1000 light-years away.
This color picture was taken in 1995 at the
Burrell-Schmidt Telescope at
Kitt Peak National Observatory in
Arizona.
The
M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year 130 AD.
Also visible is a
dark dust cloud
near the bottom of the frame,
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2002 March 17 - NGC 2244: A Star Cluster in the Rosette Nebula
Explanation:
In the heart of the
Rosette Nebula
lies a bright
open cluster
of stars that lights up the nebula.
The stars of
NGC 2244 formed from the surrounding gas only
four million years ago and emit light and
wind that define the nebula's appearance today.
High energy light from the
bright young stars of
NGC 2244 ionizes the surrounding
hydrogen gas clouds to create the red
emission nebula appearance.
The hot
wind of particles that streams away from the
cluster stars contributes to an already complex
menagerie of gas and
dust filaments while slowly
evacuating the cluster center.
NGC 2244
measures about 50
light-years across, lies about
4500 light-years away, and is visible with
binoculars towards the
constellation of Monoceros.
APOD: 2001 December 18 - Sharpless 212 in Hydrogen and Sulfur
Explanation:
Where do the most massive stars form? Observational evidence
indicates that the outskirts of developing
open clusters of stars
are primary locations.
Pictured above is one such open cluster:
Sharpless 212.
Visible in the image center are massive stars in the
open cluster.
The energetic light from these stars
ionizes surrounding
hydrogen atoms creating an
HII region.
As the hydrogen atoms re-acquire
electrons, they emit the red light highlighted.
Sharpless 212 also contains small amounts of
dust and heavy atoms such as
Sulfur.
The dust efficiently absorbs light, while emission from
Sulfur is highlighted in blue.
Particularly striking and well-defined boundaries that separate the
ionized material from surrounding neutral material
are visible at the edge of the
HII region.
Sharpless 212 spans about 20 light years and lies about 25,000
light years away.
APOD: 2001 September 9 - NGC 3293: A Bright Young Open Cluster
Explanation:
Hot blue stars
shine brightly in this beautiful,
recently formed galactic or
"open" star cluster.
Open cluster
NGC 3293 is located in the
constellation Carina, lies at a distance of about 8000
light years, and has a particularly high abundance of
these young bright stars.
A study of
NGC 3293 implies that the blue stars are
only about 6 million years old, whereas the
cluster's dimmer, redder stars appear to be
about 20 million years old.
If true, star formation in this
open cluster
took at least 15 million years.
Even this amount of time is short, however,
when compared with the billions of years stars like our
Sun live,
and the over-ten billion year lifetimes of many
galaxies and our
universe.
NGC 3293 appears just in front of a dense
dust lane
emanating from the
Carina Nebula.
APOD: 2001 August 20 - The Lagoon Nebula in Three Colors
Explanation:
The bright
Lagoon Nebula is home to a diverse array of astronomical objects.
Particularly interesting sources include a bright
open cluster of stars and
several energetic
star-forming regions.
When viewed by eye,
cluster light
is dominated by an overall red glow that is caused by
luminous hydrogen gas,
while the dark filaments are caused by absorption by dense
lanes of
dust.
The
above picture,
from the
Curtis-Schmidt Telescope,
however, shows the nebula's emission in three exact colors
specifically emitted by
hydrogen,
oxygen, and
sulfur.
The Lagoon Nebula,
also known as M8 and
NGC 6523, lies about 5000 light-years away.
The Lagoon Nebula can be located
with binoculars in the constellation of
Sagittarius spanning a region
over three times the diameter of a
full Moon.
APOD: 2001 July 30 - Star Cluster R136 Bursts Out
Explanation:
In the center of star-forming region
30 Doradus
lies a huge cluster of the largest, hottest,
most massive stars known.
Known as
R136, the cluster's
energetic stars are breaking out of the
cocoon of gas and dust from which they formed.
This disintegrating cocoon, which fills the rest of the recently released
above picture by the
Hubble Space Telescope,
is predominantly
ionized hydrogen from 30 Doradus.
R136 is composed of thousands of
hot blue stars,
some about 50 times more massive than our
Sun.
R136, also known as
NGC 2070, lies in the
LMC - a satellite galaxy to our own
Milky Way Galaxy.
Although the young ages of stars in R136 make it
similar to a Milky Way
open cluster,
its high density of stars will likely turn it into a low mass
globular cluster
in a few billion years.
APOD: 2001 June 18 - NGC 4755: A Jewel Box of Stars
Explanation:
The great variety of star colors in this
open cluster underlies its name:
The Jewel Box.
One of the bright central stars is a red supergiant,
in contrast to the many blue stars that surround it.
The cluster, also known as
Kappa Crucis contains just over 100 stars,
and is about 10 million years old.
Open clusters are younger,
contain few stars, and contain a much higher fraction of
blue stars than do
globular clusters.
This
Jewel Box lies about 7500 light-years away, so the light that we see
today was emitted from the cluster before even the
Great Pyramids in
Egypt were built.
The Jewel Box,
pictured above,
spans about 20 light-years,
and can be seen with binoculars towards the southern constellation of
Crux.
APOD: 2001 May 6 - The Pleiades Star Cluster
Explanation:
It is the most famous star cluster on the sky. The
Pleiades can be seen
without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The
Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above photograph are the blue
reflection nebulae
that surround the bright cluster
stars.
Low mass, faint,
brown dwarfs have
recently been found in the
Pleiades.
APOD: 2001 February 14 - The Rosette Nebula
Explanation:
Would the
Rosette Nebula by any other
name look as
sweet?
The bland
New General Catalog
designation of
NGC 2237 doesn't appear to diminish the
appearance of the
this flowery
emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated
NGC 2244.
These stars
formed about four million years ago from the nebular
material and their
stellar winds are clearing a hole in the nebula's center,
insulated by a layer of
dust and hot gas.
Ultraviolet light from the
hot cluster stars causes the surrounding nebula to glow.
The
Rosette Nebula spans about 100
light-years across, lies
about 5000 light-years away,
and can be seen with a small telescope towards the constellation of
Monoceros.
APOD: 2001 February 7 - Distant Open Cluster M103
Explanation:
Bright blue stars highlight the open cluster known as
M103.
The
gas clouds
from which these stars condensed has long dispersed.
Of the stars that were formed, the
brightest, bluest, and most massive have already used up their nuclear fuel and self-destructed in
supernova explosions.
A 20 million-year age for M103 was
estimated by finding the brightest
main-sequence stars
that still survive and theoretically computing their lifetimes.
In fact, a formerly blue star has recently
evolved off the
main sequence and is
visible above as the
red giant star near the cluster center.
In general, yellow stars like our
Sun are usually less
bright and hence less prominent in
open clusters
than their massive blue cousins.
Light takes about 14
years to cross
M103.
Although visible with binoculars toward the
constellation of
Cassiopeia,
M103's great distance of 8000 light years
makes it appear four times smaller than a
full moon.
APOD: 2000 October 22 - Wild Duck Open Cluster M11
Explanation:
Many
stars like our
Sun were formed in
open clusters.
The above open cluster,
M11, contains thousands of stars and is just over
three thousand
light years distant.
The stars in this cluster all formed
together about 150 million years ago.
The bright young stars in
M11 appear blue.
Open clusters, also
called galactic clusters, contain fewer and younger stars than
globular clusters.
Also unlike globular clusters,
open clusters are generally confined to the plane of
our Galaxy.
M11 is visible with binoculars towards the constellation of Scutum.
APOD: 2000 August 22 - NGC 2244: A Star Cluster in the Rosette Nebula
Explanation:
In the heart of the
Rosette Nebula
lies a bright
open cluster
of stars that lights up the nebula.
The stars of
NGC 2244 formed from the surrounding gas only
four million years ago and emit light and
wind that define the nebula's appearance today.
High energy light from the
bright young stars of
NGC 2244 ionizes the surrounding
hydrogen gas clouds to create the red
emission nebula appearance.
The hot
wind of particles that streams away from the
cluster stars contributes to an already complex
menagerie of gas and dust filaments while slowly
evacuating the cluster center.
NGC 2244
measures about 50
light-years across, lies about
4500 light-years away, and is visible with
binoculars towards the
constellation of Monoceros.
APOD: 2000 April 5 - The M7 Open Star Cluster in Scorpius
Explanation:
M7 is one of the most prominent
open clusters
of stars on the sky.
The cluster, dominated by bright blue
stars,
can be seen with the naked eye in a dark sky
in the tail of the constellation of
Scorpius.
M7 contains about 100 stars in total,
is about 200 million years old, spans 25
light-years across, and lies about 1000 light-years away.
This color picture was taken in 1995 at the
Burrell-Schmidt Telescope at
Kitt Peak National Observatory in
Arizona.
The
M7 star cluster
has been known since ancient times, being noted by
Ptolemy in the year 130 AD.
Also visible is a
dark dust cloud
near the bottom of the frame,
and literally millions of unrelated stars
towards the Galactic center.
APOD: 2000 February 27 - The Pleiades Star Cluster
Explanation:
It is the most famous star cluster on the sky. The
Pleiades can be seen
without binoculars from even the depths of a
light-polluted city.
Also known as the Seven Sisters and
M45,
the Pleiades
is one of the brightest and closest
open clusters.
The
Pleiades
contains over 3000 stars, is about 400 light years away,
and only 13 light years across.
Quite evident in the
above photograph are the blue
reflection nebulae
that surround the bright cluster
stars.
Low mass, faint,
brown dwarfs have
recently been found in the
Pleiades.
APOD: 2000 January 12 - NGC 6791: An Old, Large Open Cluster
Explanation:
NGC 6791 is one of the oldest and largest
open clusters of stars known.
But how did it get so dirty?
Open star clusters usually contain a
few hundred stars each less than a billion years old.
Open star cluster
NGC 6791, however, contains thousands of stars
recently measured to be about 8 billion years old.
What's really confusing, though, is that the stars of
NGC 6791 are relatively dirty -
the minuscule amounts of heavy
elements
(generically called metals) are high relative to most other
star clusters.
Older stars are supposed to be metal poor,
since metals have only been slowly accumulating in our
Milky Way Galaxy.
This enigma makes NGC 6791,
pictured above, one of the most studied
open clusters and a possible example of how
stars might evolve in the centers of galaxies.
APOD: October 18, 1999 - NGC 3603: An Active Star Cluster
Explanation:
NGC 3603 is home to a massive star cluster, thick dust pillars,
and a star about to explode.
The central
open cluster contains
about 2000 bright stars, each of which is much brighter
and more massive than
our Sun.
Together,
radiations from
these stars are
energizing and pushing away surrounding material, making
NGC 3603 one of the most interesting
HII regions known.
NGC 3603 is about 20,000 light-years away, and the
region shown is about 20
light-years across.
Possibly most interesting about this recently released, representative-color
picture are the large number of dim stars visible.
These stars are less massive than our Sun, demonstrating
that great numbers of low-mass stars also form in
active starburst regions.
APOD: September 21, 1999 - The Quintuplet Star Cluster
Explanation:
Bright clusters of stars form and disperse near the
center of our Galaxy.
Four million years ago the Quintuplet Cluster,
pictured above, formed and is now slowly dispersing.
The Quintuplet Cluster is located within 100
light-years of the
Galactic center,
and is home to the brightest star yet cataloged in our Galaxy: the
Pistol Star.
Objects near our
Galactic center
are usually hidden from view by opaque
dust.
This
recently-released picture was able to capture the cluster in
infrared light, though, with the
NICMOS
camera onboard the orbiting
Hubble Space Telescope.
The young
Quintuplet Cluster is one of the most massive
open clusters yet discovered,
but still much less massive than the ancient
globular clusters
that orbit in the distant halo.
Some of the bright white stars
visible above may be on the
verge
of blowing themselves up in a spectacular
supernova.
APOD: August 28, 1999 - X-Ray Pleiades
Explanation:
The Pleiades star cluster is one of the
jewels of the northern sky.
To the unaided eye it appears as
an alluring group of stars in
the constellation Taurus,
while telescopic views reveal cluster stars
surrounded by delicate blue wisps of
dust-reflected starlight.
To the X-ray telescopes
on board the orbiting
ROSAT observatory,
the cluster also presents an impressive,
but slightly altered, appearance.
This false color image was produced from ROSAT observations
by translating different
X-ray energy bands to visual colors - the lowest energies are shown
in red, medium in green, and highest energies in blue.
(The green boxes mark the position of the
seven brightest visual stars.)
The Pleiades stars seen in X-rays have extremely hot, tenuous
outer atmospheres called coronas and
the range of colors corresponds to different
coronal temperatures.
APOD: August 25, 1999 - Reflections on NGC 6188
Explanation:
NGC 6188 is an interstellar carnival of
young blue stars,
hot red gas, and
cool dark dust.
Located 4000 light years away in the
disk of our Galaxy,
NGC 6188 is home to the
Ara OB1 association, a group of bright young stars
whose nucleus forms the open cluster
NGC 6193.
These stars are so bright that some of their
blue light reflects off of
interstellar dust
forming the diffuse blue glow in the center of the
above photograph.
Open cluster NGC 6193 formed about
three million years ago from the surrounding gas,
and appears unusually rich in close binary stars.
The red glow visible throughout the photograph arises from
hydrogen gas heated by the bright stars in Ara OB1.
The dark dust that blocks much of NGC 6188's light was likely formed in the
outer atmospheres of
cooler stars and in
supernovae ejecta.
APOD: March 5, 1999 - M46 And NGC 2438: Young And Old
Explanation:
Galactic or open star clusters are relatively young.
These swarms of bright stars are born near the plane of the Milky Way,
but their numbers steadily dwindle as cluster members are
strewn through the Galaxy by gravitational interactions.
This bright open cluster, known as M46, is around 300 million years
young and still contains a few hundred stars.
Located about 5,000 light-years away toward the
constellation Puppis,
M46 is a familiar object to
telescopic stargazers
and also seems to contain a contradiction to its youthful status.
The striking red patch of glowing gas above center in this
lovely photograph
is the planetary nebula NGC 2438 - a brief,
final phase in the life of a solar-type star
a few billion years old whose central reservoir of hydrogen
fuel has been exhausted.
In fact, NGC 2438 is estimated to be only 3,000 light-years distant and
moves at a different speed than M46 cluster members.
It likely represents a foreground object, only by chance appearing
along our line of sight to young M46.
APOD: February 21, 1999 - In the Center of 30 Doradus
Explanation:
In the center of
30 Doradus
lies a huge cluster of the largest, hottest,
most massive stars known. The center of this cluster, known as
R136, is
boxed in the upper right portion of the above picture. The gas and
dust
filling the rest of the picture is predominantly ionized
hydrogen from the
emission nebula
30
Doradus. R136 is composed of thousands of hot blue
stars, some about 50 times more massive than our
Sun.
30 Doradus and R136 lie in the
LMC - a satellite galaxy to our own
Milky Way Galaxy. Although
the ages of stars in R136 cause it to be best described as an
open cluster,
R136's density will likely make it a low mass
globular cluster in a
few billion years.
APOD: January 6, 1999 - M6: The Butterfly Cluster
Explanation:
To some, the outline of the open cluster of stars M6 resembles a butterfly.
M6, also known as NGC 6405,
spans about 20 light-years and lies about
2,000 light years distant.
M6 can best be seen in a dark sky with binoculars
towards the constellation of Scorpius, coving about as much of the sky as the
full moon.
Like other open clusters, M6 is composed predominantly of
young blue stars,
although the brightest star is nearly orange.
M6 is estimated to be about 100 million years old.
Determining the distance to clusters like
M6 helps astronomers calibrate the distance scale of the universe.
APOD: December 7, 1998 - Star Forming Region RCW38
Explanation:
Star cluster RCW38 was hiding. This
open cluster of stars
is located about 5000 light years away
towards the constellation of
Vela.
Looking there will not normally reveal most of the
stars in this cluster, though. The reason is that the
open cluster is so
young that it is still shrouded in thick
dust that absorbs visible light.
This dust typically accompanies the
gas that condenses to form
young stars.
When viewed in infrared light, however, the star cluster in
RCW38
is revealed, because dust is less effective at
absorbing infrared light.
The above photograph was one of the first
ever taken with the new
Infrared Spectrometer and Array Camera (ISAAC)
affixed to the
8.2-meter Very Large Telescope.
APOD: October 25, 1998 - The Pleiades Star Cluster
Explanation:
It is the most famous star cluster on the sky. The
Pleiades can be seen
without binoculars from even the depths of a
light-polluted city.
Also known as the Seven
Sisters and
M45,
the Pleiades
is one of the
brightest and closest
open clusters. The
Pleiades
contains over 3000 stars, is about 400 light years away, and only 13 light
years across. Quite evident in the above photograph are the blue
reflection nebulae that surround the
bright cluster stars. Low mass, faint,
brown dwarfs have
recently been found in the
Pleiades.
APOD: September 21, 1998 - NGC 281: Cluster, Clouds, and Globules
Explanation:
NGC 281 is a busy workshop of star formation.
Prominent features include a small
open cluster of stars,
a diffuse red-glowing
emission nebula, large lanes of obscuring
gas and
dust, and dense knots
of dust and gas in which stars may still be forming.
The open cluster of stars IC 1590 visible on the
upper right has formed only in the last few million years.
The brightest member of this cluster is actually a
multiple-star system
shining light that helps ionize the nebula's gas,
causing the red glow visible throughout.
The lanes of dust
on the lower right might be the home of future
star formation.
Particularly striking in the
above photograph are the dark
Bok globules
visible against the bright nebula.
Stars are probably forming there right now. The entire
NGC 281 system lies about 10 thousand light years distant.
APOD: August 3, 1998 - M44: A Beehive of Stars
Explanation:
M44 is a prominent
open cluster of stars. Nicknamed
Praesepe and "The Beehive", it is one of the few
open clusters visible to the unaided eye.
M44
was thought to be a
nebula until
Galileo
used an early telescope to resolve the
cluster's bright blue stars. These stars are visible in the
above image.
M44, which is thought to have formed
about 400 million years ago, is larger and older than most
other open clusters.
The Beehive Cluster lies about 580 light-years away,
and spans about 10 light-years across.
When viewed with a powerful telescope,
hundreds of stars become visible.
APOD: April 5, 1998 - X-Ray Pleiades
Explanation:
The Pleiades star cluster is one of the
jewels of the northern sky.
To the unaided eye it appears as
a lovely and tantalizing grouping of stars in
the constellation of Taurus,
while telescopic views reveal cluster stars
surrounded by delicate blue wisps of dust-reflected starlight.
To the X-ray telescopes
on board the orbiting
ROSAT observatory,
the cluster also presents an impressive,
but slightly altered, appearance.
This false color image was produced from ROSAT observations
by translating different
X-ray energy bands to visual colors - the lowest energies are shown
in red, medium in green, and highest energies in blue.
(The green boxes mark the position of the
seven brightest visual stars.)
The Pleiades stars seen in X-rays have extremely hot, tenuous
outer atmospheres called coronas and
the range of colors corresponds to different
coronal temperatures.
APOD: March 29, 1998 - NGC 3293: A Bright Young Open Cluster
Explanation:
Hot blue stars shine brightly in
this beautiful, recently formed galactic or "open" star cluster.
Open cluster NGC
3293 is located in the constellation
Carina,
lies at a distance of about
8000 light years, and has a particularly high abundance of these young
bright stars.
A study of NGC 3293 implies that the blue stars are only about 6
million years old, whereas the cluster's
dimmer, redder stars appear to be about 20
million years old. If true, star formation in this open cluster took at
least 15 million years. Even this amount of time
is short, however, when
compared with the billions of years stars like our
Sun live, and the
over-ten billion year lifetimes of many
galaxies and our universe. NGC 3293 appears just in front dense dust lane emanating from the
Carina Nebula.
APOD: February 14, 1998 - The Rosette Nebula
Explanation:
Would the Rosette Nebula by any other name look as sweet?
The bland New General Catalog designation of NGC 2237 doesn't appear to diminish the
appearance of the this flowery emission nebula.
Inside the nebula lies an
open cluster
of bright young stars designated NGC 2244.
These stars recently formed from the nebular
material and their stellar "wind"
has cleared a hole in the nebula's center, insulated by a layer of
dust and hot
gas.
Ultraviolet
light from the hot cluster stars causes the surrounding
nebula to glow.
APOD: January 27, 1998 - The Great Nebula in Orion
Explanation:
The Great Nebula in Orion can be found just below and to
the left of the easily identifiable
belt of three stars in the popular constellation Orion.
This fuzzy patch contains one of the closest stellar nurseries,
lying at a distance of about 1500 light years.
In the above picture, the red region on the left consists of nebulae designated
M42 and M43 and contains the bright
Trapezium
open cluster.
The blue region on the right is a nebula
primarily
reflecting
the light from internal bright stars.
Recent observations of the
Orion Nebula by the
Hubble Space Telescope
have located solar-system sized
star-forming regions.
APOD: November 18, 1997 - In the Center of the Trapezium
Explanation:
Start with the constellation of Orion. Below
Orion's
belt is a fuzzy area known as the
Great Nebula of Orion or M42.
In this nebula is a bright star cluster known as the
Trapezium, shown above. New stellar systems are forming there in
gigantic globs of gas and dust known as
Proplyds.
Looking closely at the above picture also reveals that
gas and dust surrounding some of the dimmer stars
appears to form structures that point away from the brighter stars. The
above false color image
was made by combining several exposures from the
Hubble Space Telescope.
APOD: October 18, 1997 - The Pleiades Star Cluster
Explanation:
It is the most famous star cluster on the sky. The
Pleiades can be seen
without binoculars from even the depths of a
light-polluted city.
Also known as the Seven
Sisters and
M45,
the Pleiades
is one of the
brightest and closest
open clusters. The
Pleiades
contains over 3000 stars, is about 400 light years away, and only 13 light
years across. Quite evident in the above photograph are the blue
reflection nebulae that surround the
bright cluster stars. Low mass, faint,
brown dwarfs have
recently been found in the Pleiades.
APOD: October 4, 1997 - In the Center of 30 Doradus
Explanation:
In the center of
30 Doradus
lies a huge cluster of the largest, hottest,
most massive stars known. The center of this cluster, known as
R136, is
boxed in the upper right portion of the above picture. The gas and
dust
filling the rest of the picture is predominantly ionized
hydrogen from the
emission nebula
30
Doradus. R136 is composed of thousands of hot blue
stars, some about 50 times more massive than our
Sun. 30 Doradus and R136
lie in the
LMC - a satellite galaxy to our own
Milky Way Galaxy. Although
the ages of stars in R136 cause it to be best described as an
open cluster,
R136's density will likely make it a low mass
globular cluster in a
few billion years.
APOD: July 30, 1997 - Eagle Castle
Explanation:
What lights up this castle of star formation? The familiar
Eagle Nebula glows much like a
neon sign,
but in many colors at once. The
above
photograph is a composite of three of these glowing gas colors.
In particular the glowing red
Sulfur
gas of the nebula nicely outlines some of the
denser
star forming knots. Energetic light from young massive stars
causes the gas to glow and effectively boils away part of the
dust and gas from its birth pillar.
Many of these stars will
explode after several million years,
returning most of their elements back to the nebula which formed them.
This process is forming an
open cluster of stars known as
M16.
APOD: July 18, 1997 - Blue Stars and Red Pillars
Explanation:
Bright blue stars are still forming in the red pillars of the Eagle Nebula.
Made famous by a
picture from the
Hubble Space Telescope in 1995,
the
Eagle
Nebula shows the dramatic process of star formation.
To the upper right of the nebula in the
above
picture lies the heart of the
open cluster
M16. This picture closely depicts the true colors of the stars and nebula.
The bright blue stars of
M16
are continually forming from the
Eagle Nebula gas, most recently
in the famous gas and dust pillars seen below the photo's center.
Of all the young stars in
M16,
the most massive shine the brightest and the bluest.
A typical age for a star in this cluster is about 5 million years,
making them only 1/1000 the age of our
Sun.
Light takes about 7000 years to reach us from M16.
APOD: April 16, 1997 - A Star Cluster Through Hale-Bopp's Tail
Explanation: Comet Hale-Bopp continues to look impressive.
The photograph above
captured the comet on April 7th passing nearly in front
of M34,
a star cluster in the constellation of Perseus.
Many of the stars in this open cluster
can be seen through Comet Hale-Bopp's
white dust tail. The bright blue ion tail
now shows several streams. Now receding
from both the Sun and the Earth, Comet Hale-Bopp
should still remain an impressive sight
for weeks to come as it slowly fades.
APOD: January 29, 1997 - NGC 869 & NGC 884: A Double Open Cluster
Explanation: Most star clusters are singularly impressive.
But open clusters NGC 869 and NGC 884
are doubly impressive. Also known as "h and chi Persei",
this rare double cluster, shown above,
is bright enough to be seen from a dark location without even
binoculars. Although their discovery surely predates written
history, the "double cluster" was notably cataloged
by the Greek astronomer Hipparcos.
The clusters are over 7000 light years distant toward the constellation
of Perseus,
but are separated by only hundreds of light years.
APOD: January 28, 1997 - Open Cluster M50
Explanation: Many stars form in clusters. Two types of
star clusters are visible in our Milky Way Galaxy:
open clusters and globular clusters.
Open clusters like M50, shown above,
typically contain hundreds of stars,
many of which are bright, young, and blue. In fact, most of the
bright blue stars in the above picture belong to M50,
but most of the dimmer, red stars do not. M50 lies about 3000
light-years from Earth and is about
20 light years across. Open clusters
tend to have irregular shapes and are mostly found in the plane of our Galaxy.
APOD: November 11, 1996 - NGC 4755: A Jewel Box of Stars
Explanation: The great variety of star colors in this open cluster
underlie it's name: The Jewel Box. The bright central star Kappa
Crucis
is red, in contrast to the many blue stars
that surround it. The cluster contains just over 100 stars, and
might be no older than 10 million years. Open clusters
are younger, contain few stars, and contain a much higher fraction
of blue stars than do globular clusters.
This Jewel Box
lies about 7500 light-years away, so the light that we see today
was emitted from the clusters before even the Great Pyramids in Egypt
were built.
APOD: September 25, 1996 - Bright Stars and Dark Clouds
Explanation: Did you ever feel like a black cloud was following
you around? Well don't feel bad - this even happened to the bright
young stars of the open cluster NGC
6520. On the left are the cluster's bright blue stars. They
formed only millions of years ago - much more recently than our
ancient Sun
which formed billions of years ago. On the right is an absorption nebula from
which the stars might have formed. This nebula contains much
opaque dust which blocks
visible light from the many stars that would have been seen in
the background. The study of open clusters is valuable for many
reasons which include the understanding star formation
and the calibration of the distance scale of our universe.
APOD: August 23, 1996 - NGC 3293: A Bright Young Open Cluster
Explanation:
Hot Blue stars shine brightly in
this beautiful, recently formed galactic or "open" star cluster.
Open cluster NGC
3293 is located in the constellation
Carina,
lies at a distance of about
8000 light years, and has a particularly high abundance of these young
bright stars.
A study of NGC 3293 implies that the blue stars are only about 6
million years old, whereas the cluster's
dimmer, redder stars appear to be about 20
million years old. If true, star formation in this open cluster took at
least 15 million years. Even this amount of
time
is short, however, when
compared with the billions of years stars like our
Sun live, and the
over-ten billion year lifetimes of many
galaxies and our universe. NGC 3293 appears just in front dense dust lane emanating from the
Carina Nebula.
APOD: May 24, 1996 - In the Center of 30 Doradus
Explanation:
In the center of
30 Doradus
lies a huge cluster of the largest, hottest,
most massive stars known. The center of this cluster, known as
R136, is
boxed in the upper right portion of the above picture. The gas and
dust
filling the rest of the picture is predominantly ionized
hydrogen from the
emission nebula
30
Doradus. R136 is composed of thousands of hot blue
stars, some about 50 times more massive than our
Sun. 30 Doradus and R136
lie in the
LMC - a satellite galaxy to our own
Milky Way Galaxy. Although
the ages of stars in R136 cause it to be best described as an
open cluster,
R136's density will likely make it a low mass
globular cluster in a
few billion years.
APOD: May 22, 1996 - Star Cluster in the Rosette Nebula
Explanation:
Embedded in the center of the colorful and photogenic
Rosette Nebula is a bright, young
open cluster. The bright blue
stars in this cluster, labelled NGC 2244, emit
ultraviolet light that
knocks electrons away from
hydrogen atoms.
When the electrons fall back,
they emit the red light which distinctively defines the glow of all
emission nebulae. The
Rosette Nebula is thousands of light years distant,
but light would take only about 100 years to cross it. The
Rosette Nebula
is not difficult to observer and, although faint, actually appears larger
than the
full moon.
APOD: February 14, 1996 - NGC 2237: The Rosette Nebula
Explanation:
Would the
Rosette
nebula
by any other name look as sweet?
The bland
New General Catalog
designation of
NGC 2237
doesn't appear to diminish the appearance of the this flowery
emission nebula.
Inside the nebula lies an
open cluster of bright young stars
designated NGC 2244.
These stars recently formed from the nebular
material and their stellar "wind"
has cleared a hole in the nebula's center, insulated by a layer of
dust and hot
gas.
Ultraviolet
light from the hot cluster stars causes the surrounding
nebula to glow.
APOD: January 27, 1996 - Open Cluster M8 in the Lagoon
Explanation:
The large majestic
Lagoon Nebula
is home for many
young stars and
hot gas.
The Lagoon
Nebulae is so large and bright it can be seen without a telescope.
Formed only several million years ago in the nebula is the
open cluster known as NGC 6530, whose
young stars show their high temperature by
their blue glow. The nebula, also known as
M8 and NGC 6523, is named
"Lagoon"
for the band of dust seen to the left of the open cluster's center.
A bright knot of gas and dust in the nebula's center is known as the
Hourglass
Nebula. Star formation continues in the the
Lagoon
Nebula as witnessed by the many
globules that exist there.
APOD: January 16, 1996 - Wild Duck Open Cluster M11
Explanation:
Many stars like our
Sun were formed in
open
clusters. The above open cluster,
M11, contains thousands of stars and
is just over three thousand light years distant. The stars in
this cluster all
formed together about 150 million years ago. The many bright stars in the
cluster appear blue.
Open clusters, also
called galactic clusters,
contain fewer and younger stars than
globular clusters. Also unlike
globular clusters,
open clusters are generally confined to the
plane of our Galaxy.
APOD: November 1, 1995 - M16: Dust and an Open Cluster
Explanation:
The photogenic
M16 shown above is composed of a
young star cluster and a
spectacular emission nebulae
lined with distinct regions of
interstellar dust.
Most of the stars in the
cluster
can be seen offset just above and to the right of the photograph's center.
This type of star cluster is called an "open" or "galactic" cluster and
typically has a few hundred young bright members. The redness of the
surrounding
emission nebula gas is caused by
electrons recombining with hydrogen nuclei, while the dark regions are
dust lanes that absorb much of
the radiation that enters it. The dust absorbs so much light it allows
astronomers to determine which stars are inside the nebula and which are in
the foreground.