Astronomy Picture of the Day |
APOD: 2024 July 14 – Meteor Misses Galaxy
Explanation:
The galaxy was never in danger.
For one thing, the
Triangulum galaxy (M33), pictured,
is much bigger than the
tiny grain of rock
at the head of the meteor.
For another, the galaxy is much farther away -- in this instance 3 million
light years as opposed to only about 0.0003 light seconds.
Even so, the
meteor's path
took it angularly below the galaxy.
Also the wind high in
Earth's atmosphere blew the
meteor's glowing evaporative molecule train away from the galaxy, in angular projection.
Still, the astrophotographer was quite lucky to capture
both a meteor and a galaxy in a single exposure -- which was subsequently added to two other images of
M33 to bring up the
spiral galaxy's colors.
At the end,
the meteor was gone in a second, but
the galaxy will last billions of years.
APOD: 2024 June 3 - NGC 2403 in Camelopardalis
Explanation:
Magnificent island universe
NGC 2403
stands within the boundaries of the long-necked constellation
Camelopardalis.
Some 10 million light-years distant and about 50,000 light-years
across, the spiral galaxy also seems to have more
than its fair share of giant star forming
HII regions,
marked by the telltale reddish glow of atomic hydrogen gas.
The giant HII regions are energized by clusters of hot, massive stars
that explode as
bright supernovae
at the end of their short and furious lives.
A member of the M81 group of galaxies,
NGC 2403 closely resembles a galaxy in our own local galaxy group with an
abundance of star forming regions,
M33, the Triangulum Galaxy.
Spiky in appearance,
bright stars in
this portrait of NGC 2403
are in the foreground, within our own Milky Way.
Also in the foreground of the deep, wide-field, telescopic
image are the Milky Way's dim and dusty
interstellar clouds also known as
galactic cirrus or integrated flux nebulae.
But faint features that seem to extend from
NGC 2403 itself
are likely tidal stellar streams drawn out by gravitational interactions
with neighboring galaxies.
APOD: 2024 April 25 - NGC 604: Giant Stellar Nursery
Explanation:
Located some 3 million light-years away in the arms of nearby spiral
galaxy M33,
giant stellar nursery
NGC 604 is
about 1,300 light-years across.
That's nearly 100 times the size of the Milky Way's
Orion Nebula, the closest large star forming
region to planet Earth.
In fact, among the star forming regions within the Local Group of
galaxies, NGC 604 is second in size only to 30 Doradus,
also known as
the Tarantula Nebula in the
Large Magellanic Cloud.
Cavernous bubbles and cavities in NGC 604
fill this stunning infrared image from the
James Webb Space Telescope's NIRCam.
They are carved out by energetic stellar winds
from the region's
more than 200 hot, massive, young stars, all still in early
stages of their lives.
APOD: 2023 October 13 - Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy Messier 33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies a mere 3 million light-years away.
The galaxy's central 30,000 light-years or so are shown in this
sharp galaxy portrait.
The portrait features M33's
reddish ionized hydrogen clouds or
HII regions.
Sprawling along loose spiral arms that wind toward the core,
M33's giant HII regions
are some of the largest known stellar nurseries,
sites of the formation of short-lived but very massive stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding hydrogen gas and ultimately produces the
characteristic red glow.
In this image, broadband data were combined
with narrowband data recorded through a hydrogen-alpha filter.
That filter transmits the light of the strongest visible hydrogen
emission line.
APOD: 2023 April 12 - NGC 206 and the Star Clouds of Andromeda
Explanation:
The large stellar association cataloged as
NGC 206 is
nestled within the dusty arms of the neighboring
Andromeda galaxy
along with the galaxy's pinkish star-forming regions.
Also known as M31,
the spiral galaxy is a mere
2.5 million light-years away.
NGC 206 is found right of center in
this sharp and detailed close-up of the southwestern
extent of
Andromeda's disk.
The bright, blue
stars of NGC 206
indicate its youth.
In fact, its youngest massive stars are less than 10 million years old.
Much larger than the open or galactic clusters of young stars
in the disk of our Milky Way galaxy,
NGC 206
spans about 4,000 light-years.
That's comparable in size to the giant stellar nurseries
NGC 604 in nearby spiral
M33 and the
Tarantula Nebula
in the Large Magellanic Cloud.
APOD: 2022 November 3 - M33: The Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About
3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from the Milky Way,
this
sharp image combines data from telescopes on and around planet
Earth to show off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604
is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance
scale of the Universe.
APOD: 2021 November 12 - M33: The Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this sharp image
shows off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604 is the
brightest star forming region, seen here at about the 4 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance
scale of the Universe.
APOD: 2021 November 6 - The Galaxy Between Two Friends
Explanation:
On an August night two friends
enjoyed this view after
a day's hike on the Plateau d'Emparis in the French Alps.
At 2400 meters altitude the sky was clear.
Light from a setting moon illuminates the foreground
captured in the simple vertical panorama of images.
Along the plane of our Milky Way galaxy
stars of Cassiopeia and Perseus shine along the panorama's left edge.
But seen as a faint cloud with a brighter core, the
Andromeda galaxy,
stands directly above the two friends in the night.
The nearest large spiral galaxy, Andromeda is about
2.5 million light-years beyond the stars of the Milky Way.
Adding to the evening's shared
extragalactic
perspective, the fainter fuzzy spot in the sky right between them is
M33, also known as the Triangulum galaxy.
Third largest in the
local galaxy group, after Andromeda and
Milky Way, the Triangulum galaxy is about 3 million light-years distant.
On that night, the two friends stood about 3
light-nanoseconds
apart.
APOD: 2021 September 30 - The Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy M33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies a mere 3 million light-years away.
Sprawling along loose spiral arms that wind toward the core,
M33's giant
HII regions are
some of the largest known stellar nurseries,
sites of the formation of short-lived but very massive stars.
Intense ultraviolet radiation
from the luminous massive stars ionizes
the surrounding hydrogen gas and
ultimately produces the characteristic red glow.
To highlight the HII regions in this telescopic image,
broadband data used to produce a color view
of the galaxy were combined with narrowband data recorded through a
hydrogen-alpha filter,
transmitting the light of the strongest
hydrogen emission line.
Close-ups of cataloged HII regions appear in the sidebar insets.
Use the individual reference number to
find their location within the Triangulum Galaxy.
For example, giant
HII region NGC604
is identified in an inset on the right and appears at position number 15.
That's about 4 o'clock from galaxy center in
this portrait of M33.
APOD: 2021 September 8 - The Deep Sky Toward Andromeda
Explanation:
What surrounds the Andromeda galaxy?
Out in space, Andromeda (M31) is closely surrounded by several small
satellite galaxies, and further out it is part of the
Local Group of Galaxies -- of which our Milky Way galaxy is also a member.
On the sky, however, gas clouds local to
our Milky Way appear to surround M31 --
not unlike how water clouds in
Earth's atmosphere may appear to
encompass our Moon.
The gas clouds toward Andromeda,
however, are usually too faint to see.
Enter the
featured 45-degree long image
-- one of the deeper images yet taken of the
broader Andromeda region.
This image, sensitive to light specifically
emitted by hydrogen gas, shows these faint and unfamiliar clouds in
tremendous detail.
But the image captures more.
At the image top is the
Triangulum galaxy (M33),
the third largest galaxy in the
Local Group and the furthest object that can be seen with the unaided eye.
Below M33 is the bright Milky-Way star
Mirach.
The image is the digital accumulation of
several long exposures taken from 2018 to 2021 from
Pulsnitz,
Germany.
APOD: 2019 December 31 - M33: The Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
sharp image
shows off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604 is the
brightest star forming region, seen here at about the 7 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance scale of the Universe.
APOD: 2019 October 3 - The Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy M33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies a mere 3 million light-years away.
The galaxy's inner 30,000 light-years or so are shown in this
magnificent 25 panel telescopic mosaic.
Based on image data from space and ground-based telescopes,
the portrait of M33 shows off the galaxy's reddish ionized hydrogen
clouds or HII
regions.
Sprawling along loose spiral arms that wind toward the core,
M33's
giant HII regions are some of the largest known
stellar nurseries, sites of the formation of short-lived
but very massive stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding hydrogen gas and ultimately produces the
characteristic red glow.
To enhance this image, broadband data were used to produce a color view
of the galaxy and combined with narrowband data recorded through a
hydrogen-alpha filter.
That filter transmits the light of the strongest visible hydrogen
emission
line.
APOD: 2019 April 30 - Meteor Misses Galaxy
Explanation:
The galaxy was never in danger.
For one thing, the
Triangulum galaxy (M33), pictured,
is much bigger than the
tiny grain of rock
at the head of the meteor.
For another, the galaxy is much farther away -- in this instance 3 million
light years as opposed to only about 0.0003 light seconds.
Even so, the
meteor's path
took it angularly below the galaxy.
Also the wind high in
Earth's atmosphere blew the
meteor's glowing evaporative molecule train away from the galaxy, in angular projection.
Still, the astrophotographer was quite lucky to capture
both a meteor and a galaxy in a single exposure -- which was subsequently added to two other images of M33 to bring up the
spiral galaxy's colors.
At the end,
the meteor was gone in a second, but
the galaxy will last billions of years.
APOD: 2019 February 23 - The Stars of the Triangulum Galaxy
Explanation:
Like
grains of sand on a cosmic beach, stars of the Triangulum Galaxy
are resolved in this sharp mosaic from the Hubble Space Telescope's
Advanced Camera for Surveys
(ACS).
The inner region of the galaxy spanning over
17,000 light-years is covered at extreme resolution, the
second
largest image ever released by Hubble.
At its center is the bright, densely packed galactic core surrounded by
a loose array of dark dust lanes mixed with the stars in
the galactic plane.
Also known as M33, the face-on spiral galaxy lies 3 million light-years
away in the small northern constellation Triangulum.
Over 50,000 light-years in diameter, the
Triangulum Galaxy is the
third largest in the
Local Group
of galaxies after the Andromeda Galaxy (M31), and our own Milky Way.
Of course, to fully appreciate the Triangulum's stars, star clusters,
and bright nebulae captured in this Hubble mosaic, you'll need to
use a
zoom tool.
APOD: 2018 September 27 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
sharp image
shows off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604 is the
brightest star forming region, seen here at about the 7 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance scale of the Universe.
APOD: 2017 November 30 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this
sharp composite image nicely shows off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604 is the
brightest star forming region, seen here at about the 7 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance scale of the Universe.
APOD: 2016 October 7 - The Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy M33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies about 3 million light-years distant.
The galaxy's inner 30,000 light-years or so are shown in this
telescopic
portrait that enhances its reddish ionized hydrogen
clouds or HII
regions.
Sprawling along loose spiral arms that wind toward the core,
M33's
giant HII regions are some of the largest known
stellar nurseries, sites of the formation of short-lived
but very massive stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding hydrogen gas and ultimately produces the
characteristic red glow.
To enhance this image, broadband data was used to produce a color view
of the galaxy and combined with narrowband data recorded through a
hydrogen-alpha filter.
That filter transmits the light of the strongest visible hydrogen
emission line.
APOD: 2016 October 6 - Trifid, Lagoon, and Mars
Explanation:
Bright
nebulae and star clusters along this 5 degree
wide field of view are popular stops on telescopic tours
of the constellation Sagittarius and the crowded starfields of
the central Milky Way.
Cataloged by 18th century French
astronomer Charles Messier, M20, the colorful Trifid Nebula,
and M8, the expansive Lagoon Nebula, are at upper left and center.
Both are well-known
star forming regions about 5,000 light-years distant.
Just passing through the same
field of view on September 29,
the yellowish star lined up with M8 and M20 at the lower right is
actually Mars,
close to 8.8 light-minutes from Earth on that date.
That distance is nearly
equivalent
to 1 astronomical unit or the distance from Earth to Sun.
Mars is overexposed in the image,
with visible diffraction spikes created by the telescope mirror supports.
Of course, Mars has long been
known to wander through planet Earth's
night skies.
APOD: 2016 September 17 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this sharp
composite image nicely shows off M33's blue star clusters
and pinkish star forming regions along
the galaxy's loosely wound spiral arms.
In fact, the
cavernous NGC 604 is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a cosmic yardstick for
establishing
the distance scale of the Universe.
APOD: 2016 February 19 - NGC 2403 in Camelopardalis
Explanation:
Magnificent island universe
NGC 2403
stands within the boundaries of the long-necked constellation
Camelopardalis.
Some 10 million light-years distant and about 50,000 light-years
across, the spiral galaxy also seems to have more
than its fair share of giant star forming
HII regions,
marked by the telltale reddish glow of atomic hydrogen gas.
The giant HII regions are energized by clusters of hot, massive stars
that explode as
bright supernovae
at the end of their short and furious lives.
A member of the M81 group of galaxies,
NGC 2403 closely resembles another galaxy with an
abundance of star forming regions that lies
within our own local galaxy group,
M33 the Triangulum Galaxy.
Spiky in appearance,
bright stars in this colorful galaxy
portrait of NGC 2403
are in the foreground, within our own Milky Way.
APOD: 2015 September 26 - M31 versus M33
Explanation:
Separated by about 14 degrees
(28 Full Moons) in planet Earth's sky,
spiral galaxies M31 at left, and M33 are both large members of
the Local
Group, along with our own Milky Way galaxy.
This narrow- and wide-angle,
multi-camera
composite finds details of spiral structure
in both, while the massive neighboring galaxies seem to be balanced
in starry fields either side of
bright Mirach, beta star in
the constellation Andromeda.
Mirach is just 200 light-years from the Sun.
But M31, the Andromeda Galaxy,
is really 2.5 million light-years distant and
M33, the Triangulum Galaxy, is also about
3 million light years away.
Although they look far apart,
M31 and M33 are engaged in a gravitational struggle.
In fact, radio astronomers have
found indications of
a bridge of neutral hydrogen gas that could connect the two,
evidence of a closer encounter in the past.
Based on measurements, gravitational
simulations currently
predict that the Milky Way, M31, and M33
will all undergo mutual close encounters and potentially
mergers, billions of years
in the future.
APOD: 2015 March 27 - NGC 2403 in Camelopardalis
Explanation:
Magnificent island universe
NGC 2403
stands within the boundaries
of the long-necked constellation
Camelopardalis.
Some 10 million light-years distant and about 50,000 light-years
across, the spiral galaxy also seems to have more
than its fair share of giant star forming
HII regions,
marked by the telltale reddish glow of atomic hydrogen gas.
The giant HII regions are energized by clusters of hot, massive stars
that explode as
bright supernovae
at the end of their short and furious lives.
A member of the M81 group of galaxies,
NGC 2403 closely resembles another galaxy with an
abundance of star forming regions that lies
within our own local galaxy group,
M33 the Triangulum Galaxy.
Spiky in appearance,
bright stars in this colorful galaxy portrait of NGC 2403
lie in the foreground, within our own Milky Way.
APOD: 2014 September 25 - NGC 206 and the Star Clouds of Andromeda
Explanation:
The large stellar association cataloged as
NGC 206 is
nestled within the dusty arms of the neighboring
Andromeda galaxy.
Also known as M31,
the spiral galaxy is a mere
2.5 million light-years away.
NGC 206 is near top center in
this
gorgeous close-up of the southwestern
extent of
Andromeda's disk, a remarkable composite of data from
space and ground-based observatories.
The bright, blue
stars of
NGC 206 indicate its youth.
In fact, its youngest massive stars are less than 10 million years old.
Much larger than the open or galactic clusters of young stars
in the disk of our Milky Way galaxy,
NGC 206
spans about 4,000 light-years.
That's comparable in size to the giant stellar nurseries
NGC 604 in nearby spiral
M33 and the
Tarantula Nebula,
in the Large Magellanic Cloud.
Star forming sites within Andromeda are revealed by the telltale
reddish emission from clouds of ionized hydrogen gas.
APOD: 2013 December 26 - The Hydrogen Clouds of M33
Explanation:
Gorgeous spiral galaxy M33 seems to have more than its fair share of
glowing hydrogen gas.
A prominent member of the local group of galaxies, M33 is also
known as the Triangulum Galaxy and
lies about 3 million light-years distant.
Its inner 30,000 light-years are shown in this
telescopic
galaxy portrait
that enhances the reddish ionized hydrogen
clouds or HII regions.
Sprawling along loose spiral arms that wind toward the core,
M33's giant HII regions are some of the
largest known stellar nurseries,
sites of the formation of short-lived but very massive stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes the
surrounding hydrogen gas and ultimately produces the characteristic red
glow.
To enhance this image, broadband data was used to produce a color view
of the galaxy and combined with narrowband data recorded through a
hydrogen-alpha filter, transmitting the light of the strongest hydrogen
emission line.
To see the monochromatic narrowband data alone,
move your cursor over the image, or take this
video tour of the hydrogen clouds
of M33.
APOD: 2013 September 26 - M31 versus M33
Explanation:
Separated by about 14 degrees
(28 Full Moons) in planet Earth's sky,
spiral galaxies M31, left, and M33 are both large members of
the Local Group,
along with our own Milky Way galaxy.
This wide-angle,
telescopic mosaic captures colorful details of spiral structure
in both, while the massive neighboring galaxies seem to be balanced
either side of bright Mirach, beta star in the
constellation Andromeda.
But M31, the Andromeda Galaxy,
is really 2.5 million light-years distant and
M33, the Triangulum Galaxy, is also about
3 million light years away.
Mirach, just 200 light-years from the Sun,
lies well within the Milky Way, along with the
dim
clouds of dust drifting through the frame only a few hundred
light-years above the galactic plane.
Although they look far apart,
M31 and M33 are locked in a mutual gravitational embrace.
Radio astronomers have
found indications of
a bridge of neutral hydrogen gas that could connect the two,
evidence of a closer encounter in the past.
Based on measurements, gravitational
simulations currently
predict that the Milky Way, M31, and M33
will all undergo mutual close encounters and potentially
mergers, billions of years
in the future.
APOD: 2012 December 20 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum
Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this
sharp composite image, a 25 panel mosaic,
nicely shows off M33's blue star clusters
and pinkish star forming regions that
trace the galaxy's loosely wound spiral arms.
In fact, the cavernous NGC 604 is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2012 December 11 - NGC 604: Giant Stellar Nursery
Explanation:
Stars are sometimes born in the midst of chaos.
About 3 million years ago in the nearby galaxy
M33, a large cloud of gas
spawned dense internal knots which gravitationally
collapsed to form stars.
NGC 604 was so large, however, it could form enough stars to make a
globular cluster.
Many young stars from
this cloud are visible in the
above image from the
Hubble Space Telescope,
along with what is left of the initial
gas cloud.
Some stars were so massive they have already
evolved and exploded in a
supernova.
The brightest stars that are left emit light
so energetic that they create one of the largest clouds of
ionized hydrogen gas known,
comparable to the
Tarantula Nebula in our
Milky Way's close neighbor, the
Large Magellanic Cloud.
APOD: 2012 October 24 - NGC 206 and the Star Clouds of Andromeda
Explanation:
The large stellar association cataloged as
NGC 206 is
nestled within the dusty arms of neighboring
spiral galaxy
Andromeda (M31), 2.5 million light-years distant.
Seen near the center of
this
gorgeous close-up of the southwestern
extent of
Andromeda's disk, the bright, blue
stars of
NGC 206 indicate its youth.
Its youngest massive stars are less than 10 million years old.
Much larger than the clusters of young stars
in the disk
of our Milky Way galaxy known as open or galactic clusters,
NGC 206
spans about 4,000 light-years.
That's comparable in size to the giant stellar nurseries
NGC 604 in nearby spiral
M33 and the
Tarantula Nebula,
in the Large Magellanic Cloud.
APOD: 2011 July 23 - NGC 2403 in Camelopardalis
Explanation:
Magnificent island universe
NGC 2403 stands
within the boundaries
of the long-necked constellation
Camelopardalis.
Some 10 million light-years distant and about 50,000 light-years
across, the spiral galaxy also seems to have more
than its fair share of giant star forming
HII regions,
marked by the telltale reddish glow of atomic hydrogen gas.
In fact, NGC 2403 closely resembles another galaxy with an
abundance of star forming regions that lies
within our own local galaxy group,
M33
the Triangulum Galaxy.
Of course, supernova explosions
follow close on the heels of
the formation of
massive, short-lived stars and
in 2004 one of the brightest supernovae discovered in recent
times was found in NGC 2403.
Easy to confuse with a foreground star in our own Milky Way Galaxy,
the powerful supernova
is seen here as the spiky, bright "star" at
the left edge
of the field.
This stunning cosmic portrait
is a composite of space and ground-based
image data from the Hubble Legacy Archive
and the 8.2 meter Subaru Telescope at the summit of
Mauna Kea, Hawaii.
APOD: 2011 February 21 - Milky Way Over Switzerland
Explanation:
What's visible in the night sky during this time of year?
To help illustrate the answer, a beautiful land, cloud, and skyscape was captured earlier this month over
Neuchâtel,
Switzerland.
Visible in the foreground were the snow covered cliffs of the amphitheater shaped
Creux du Van, as well as distant trees, and town-lit clouds.
Visible in the night sky (at midnight) were galaxies including the
long arch of the central band of our
Milky Way Galaxy, the
Andromeda galaxy (M31), and the
Triangulum galaxy
(M33).
Star clusters visible included NGC 752,
M34,
M35,
M41,
the double cluster, and
the Beehive (M44).
Nebulas visible included the Orion Nebula
(M42),
NGC 7822,
IC 1396, the
Rosette Nebula,
the Flaming Star Nebula, the
California Nebula, the
Heart and
Soul Nebulas, and the
Pacman Nebula.
Rolling your cursor over the
above image will bring up labels for
all of these.
But the above
wide angle sky image captured even more sky wonders.
What other nebulas
can you find in the above image?
APOD: 2010 December 3 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum
Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth,
this sharp, detailed image
nicely shows off M33's blue star clusters
and pinkish star forming regions that
trace the galaxy's loosely wound spiral arms.
In fact, the
cavernous
NGC 604 is the
brightest star forming region, seen here at about the 4 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2009 October 17 - Bright Nebulae in M33
Explanation:
Gorgeous spiral
galaxy M33 seems to have more than its fair share
of bright emission nebulae.
In fact, narrow-band and broad-band
image
data are combined in this beautifully detailed composite to trace
the reddish emission nebulae, star forming
HII regions,
sprawling along loose spiral arms that wind toward the galaxy's core.
Historically of
great interest to astronomers, M33's
giant HII regions are some of the
largest known stellar nurseries -
sites
of the formation of short-lived but very
massive
stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding gas and ultimately produces the characteristic red glow.
Spanning over 50,000 light-years and a prominent member of the
local group of
galaxies, M33 is also known as the
Triangulum Galaxy.
It lies about 3 million light-years distant.
APOD: 2009 February 12 - Zodiacal Light Vs. Milky Way
Explanation:
Two fundamental planes of planet Earth's sky compete
for attention in this remarkable wide-angle vista,
recorded on January 23rd.
Arcing above the horizon and into the night at the left
is a beautiful band of
Zodiacal Light - sunlight scattered by
dust
in the solar system's ecliptic plane.
Its opponent on the right is composed of the
faint stars, dust clouds, and nebulae along
the plane of our
Milky Way Galaxy.
Both celestial bands stand above the domes and towers of the
Teide Observatory
on the island of Tenerife.
Also out to play in the pristine, dark skies over the Canary Islands,
are brilliant Venus (lower left),
the distant
Andromeda Galaxy (near center),
and the lovely
Pleiades star cluster (top center).
Of course, seasoned skygazers might even spot
M33, the
California Nebula,
IC1805, and the
double star cluster of Perseus.
(Need some help? Just slide your cursor over the picture.)
APOD: 2009 February 5 - NGC 604: X-rays from a Giant Stellar Nursery
Explanation:
Some 3 million light-years distant in nearby spiral
galaxy M33,
giant stellar nursery
NGC 604 is
about 1,300 light-years across,
or nearly 100 times the size of the
Orion Nebula.
In fact, among the star forming regions within the Local Group of
galaxies, NGC 604 is second in size only to 30 Doradus,
also known as
the Tarantula Nebula in the
Large Magellanic Cloud.
This space-age
color composite of X-ray data (in blue hues)
from the Chandra Observatory, and
Hubble optical data
shows that NGC 604's cavernous bubbles and cavities are filled with a
hot, tenuous,
X-ray
emitting gas.
Intriguingly, NGC 604 itself is divided by
a wall of relatively cool gas.
On the western (right) side of the nebula,
measurements
indicate that material is likely
heated to X-ray temperatures by the energetic winds
from a cluster of about 200 young, massive stars.
On the eastern side the X-ray filled cavities seem to be older,
suggesting
supernova explosions from the end of
massive star evolution contribute to their formation.
APOD: 2008 September 13 - M33: Triangulum Galaxy
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum
Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
sharp, detailed
image nicely shows off M33's blue star clusters
and pinkish star forming regions that
trace the galaxy's loosely wound spiral arms.
In fact, the cavernous NGC 604 is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2008 September 9 - M110: Satellite of the Andromeda Galaxy
Explanation:
Our Milky Way Galaxy is not alone.
It is part of a gathering of about 25 galaxies known as the
Local Group.
Members include the
Great Andromeda Galaxy (M31),
M32,
M33, the
Large Magellanic Cloud, the
Small Magellanic Cloud,
Dwingeloo 1, several small
irregular galaxies,
and many
dwarf elliptical and
dwarf spheroidal galaxies.
Pictured
on the lower right is one of the
dwarf
ellipticals:
NGC 205.
Like
M32,
NGC 205
is a companion to the large M31,
and can sometimes be seen to the south of
M31's center in photographs.
The image shows
NGC 205 to be unusual
for an elliptical galaxy
in that it contains at least two
dust clouds
(at 9 and 2 o'clock - they are visible but hard to spot)
and signs of recent star formation.
This galaxy is sometimes known as M110,
although it was actually not part of
Messier's original
catalog.
APOD: 2008 January 2 - A Galaxy is not a Comet
Explanation:
This gorgeous galaxy and comet portrait
was recorded on December 30th,
in the skies over Hoogeveen, The Netherlands.
The combined series of 60 x 60 second exposures finds
the lovely green coma of
Comet 8P/Tuttle
near its predicted conjunction with the
Triangulum
Galaxy.
Aligning each exposure with the stars shows the comet as a
streak, slowly moving against the background stars and galaxy.
An alternative
composition with exposures centered on the comet, shows the background
stars and galaxy as streaks.
The alluring celestial scene would also have been a
rewarding one for the influential 18th century comet
hunter Charles Messier.
While Messier scanned French skies for comets,
he carefully cataloged positions of things which were
fuzzy and comet-like
in appearance but did not move against the background stars and
so were definitely not comets.
The Triangulum Galaxy,
also known as M33, is the 33rd object in his famous
not-a-comet catalog.
The modern
understanding
holds that the Triangulum Galaxy is a large spiral galaxy
some 3 million light-years distant.
Comet 8P/Tuttle, just bright enough to be
visible to the unaided eye in dark,
northern skies,
is about 40 million kilometers (2 light-minutes) away.
APOD: 2007 August 25 - Just Passing Through
Explanation:
M33 is
a big, beautiful spiral galaxy a mere 3 million light-years
away, understandably a popular target for enthusiastic
astro-imagers.
Just as understandably, interfering
satellite
trails and
airplane streaks that are
becoming more common in
planet Earth's busy night sky are
processed out of their
finished images.
But Robert Stephan left these streaks in his
final
picture of M33, realizing that he had also recorded
something relatively rare.
His otherwise cosmic skyscape shows the tail of
an aircraft passing overhead through his telescope's field of view.
A navigational
strobe light
on the plane
flashed across the tail at exactly the right moment.
The brief illumination produced the incongruous,
though remarkably sharp image.
APOD: 2006 November 23 - Hydrogen in M33
Explanation:
Gorgeous spiral
galaxy M33 seems to have more than its fair share
of hydrogen.
Its inner 30,000 light-years
are shown here in an image processed
to fully reveal the reddish glow of ionized hydrogen regions
(HII regions)
sprawling along loose
spiral arms that wind toward the galaxy's core.
Historically of
great interest to astronomers, M33's
giant HII regions are some of the
largest known stellar
nurseries - sites
of the formation of short-lived but very
massive
stars.
Intense ultraviolet radiation from the luminous, massive stars ionizes
the surrounding hydrogen gas and ultimately produces the
characteristic red glow.
A prominent member of the
local group of
galaxies,
M33 is also known as the
Triangulum Galaxy
and lies about 3 million light-years distant.
APOD: 2006 September 14 - M33: Spiral Galaxy in Triangulum
Explanation:
The small, northern constellation
Triangulum
harbors this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum
Galaxy.
M33 is over 50,000 light-years in diameter, third largest in the
Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way,
M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
detailed,
wide field image nicely shows off M33's blue
star clusters
and pinkish star forming regions which
trace the galaxy's loosely wound spiral arms.
In fact, the cavernous NGC 604 is the
brightest star forming region, seen here at about the 1 o'clock position
from the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2004 December 14 - Nearby Spiral M33
Explanation:
Spiral galaxy M33 is a mid-sized member of our
Local Group of Galaxies.
M33 is also called the
Triangulum Galaxy for the constellation in which it resides.
About four times smaller (in radius) than our
Milky Way Galaxy
and the Andromeda Galaxy (M31),
it is much larger than the many of the local
dwarf spheroidal galaxies.
M33's proximity to
M31 causes it to be
thought by some to be a satellite galaxy
of this more massive galaxy.
M33's proximity to our
Milky Way Galaxy
causes it to appear more than twice the angular size of the
Full Moon, and be
visible with a good pair of binoculars.
APOD: 2003 December 9 - NGC 604: Giant Stellar Nursery
Explanation:
Stars are sometimes born in the midst of chaos.
About 3 million years ago in the nearby galaxy
M33, a large cloud of gas
spawned dense internal knots which gravitationally
collapsed to form stars.
NGC 604 was so large, however, it could form enough stars to make a
globular cluster.
Many young stars from this cloud are visible in the
above image from the
Hubble Space Telescope,
along with what is left of the initial
gas cloud.
Some stars were so massive they have already
evolved and exploded in a
supernova.
The brightest stars that are left emit light
so energetic that they create one of the largest cloud of
ionized hydrogen gas known,
comparable to the
Tarantula Nebula in our
Milky Way's close neighbor, the
Large Magellanic Cloud.
APOD: 2003 September 24 - M33: Spiral Galaxy in Triangulum
Explanation:
The small constellation
Triangulum
in the northern sky harbors
this magnificent face-on spiral galaxy, M33.
Its popular names include the Pinwheel Galaxy or just
the Triangulum Galaxy.
M33's diameter spans over 50,000 light-years, making it third largest in
the Local
Group of galaxies after the Andromeda Galaxy (M31), and our
own Milky Way.
About 3 million light-years from the Milky Way, M33
lies very close to the Andromeda Galaxy and
observers
in these two galaxies would likely have spectacular views of
each other's grand spiral star systems.
As for the view from planet Earth, this
sharp
27 frame mosaic of M33 nicely shows off blue star clusters
and pinkish star forming regions which trace the galaxy's
loosely wound spiral arms.
In fact, the cavernous NGC 604 is the brightest
star forming region seen here, visible
along an arm arcing above and to the right
of the galaxy center.
Like M31, M33's population of well-measured variable stars
have helped make this nearby spiral a
cosmic
yardstick for
establishing
the distance scale of the Universe.
APOD: 2003 July 27 -The Aquarius Dwarf
Explanation:
Our Milky Way Galaxy is not alone.
It is part of a gathering of about 50 galaxies known as the
Local Group.
Members include the
Great Andromeda Galaxy (M31),
M32,
M33, the
Large Magellanic Cloud, the
Small Magellanic Cloud,
Dwingeloo 1, several small
irregular galaxies,
and many
dwarf elliptical and
dwarf spheroidal galaxies.
Pictured above is the
Aquarius Dwarf, a faint dwarf irregular galaxy over 3 million
light years away.
An earlier
APOD
erroneously identified the above image as the
Sagittarius Dwarf.
APOD: 2002 December 2 - Nearby Spiral M33
Explanation:
Spiral galaxy M33 is a mid-sized member of our
Local Group of Galaxies.
M33 is also called the
Triangulum Galaxy for the
constellation in which it resides.
About four times smaller (in radius) than our
Milky Way Galaxy
and the Andromeda Galaxy (M31),
it is much larger than the many of the local
dwarf spheroidal galaxies.
M33's proximity to
M31 causes it to be
thought by some to be a satellite galaxy
of this more massive galaxy.
M33's proximity to our
Milky Way Galaxy
causes it to appear more than twice the angular size of the
Full Moon, and be
visible with a good pair of binoculars.
The
above high-resolution image from the
0.90-m telescope
at Kitt Peak National Observatory is a four-color composite.
APOD: 2002 November 2 - NGC 604: Giant Stellar Nursery
Explanation:
Scattered within
this
cavernous nebula, cataloged as
NGC 604,
are over 200 newly formed hot, massive, stars.
At 1,500 light-years across, this expansive cloud of interstellar gas
and dust is effectively a giant
stellar nursery located some three million light-years distant in
the spiral galaxy, M33.
The newborn stars irradiate the gas with
energetic ultraviolet light
stripping electrons from atoms and producing a
characteristic
nebular glow.
The
details
of the nebula's structure hold
clues to the mysteries of star formation and galaxy evolution.
APOD: 2002 February 2 - Centaurus A: The Galaxy Deep Inside
Explanation:
Deep inside Centaurus A, the closest
active galaxy to Earth, lies ... another galaxy!
Cen A is a giant elliptical galaxy a mere 10 million light-years
distant
with a central jumble
of stars, dust, and gas that probably hides
a massive black hole.
This composite combines an optical picture of Cen A with dark
lines tracing lobes of radio emission and an
infrared image from the
ISO
satellite (in red).
The
ISO data maps out the dust in what appears to be
a barred spiral galaxy
about the size of the prominent
nearby spiral M33.
The discoverers believe that the giant elliptical's gravity helps this
barred spiral galaxy maintain its shape.
In turn, material funneled along the spiral's bar fuels the central black hole
which powers the elliptical's radio lobes.
This apparently intimate association between two distinct
and dissimilar galaxies suggests a truly
cosmic symbiotic relationship.
APOD: 2001 September 27 - Elements of Nearby Spiral M33
Explanation:
Spiral galaxy M33 is a mid-sized member of our
Local Group of Galaxies.
M33 is also called the
Triangulum Galaxy for the
constellation in which it resides.
About four times smaller (in radius) than our
Milky Way Galaxy
and the Andromeda Galaxy (M31),
it is much larger than the many of the local
dwarf spheroidal galaxies.
M33's proximity to
M31 causes it to be
thought by some to be a satellite galaxy
of this more massive galaxy.
M33's proximity to our
Milky Way Galaxy
causes it to appear more than twice the angular size of the
Full Moon, and be
visible with a good pair of binoculars.
The
above high-resolution image highlights light emitted by
hydrogen in red and
oxygen in blue.
It was taken to help separate stars from
emission nebulae,
and therefore help
study how galaxies form stars.
APOD: 2000 October 23 - Dwarf Elliptical Galaxy NGC 205 in the Local Group
Explanation:
Our Milky Way Galaxy is not alone.
It is part of a gathering of about 25 galaxies known as the
Local Group.
Members include the
Great Andromeda Galaxy (M31),
M32,
M33, the
Large Magellanic Cloud, the
Small Magellanic Cloud,
Dwingeloo 1, several small
irregular galaxies,
and many
dwarf elliptical and
dwarf spheroidal galaxies.
Pictured on the lower left is one of the many
dwarf ellipticals:
NGC 205.
Like
M32,
NGC 205 is a companion to the large M31,
and can sometimes be seen to the south of
M31's center in photographs.
The above image shows
NGC 205 to be unusual for an
elliptical galaxy
in that it contains at least two
dust clouds
(at 1 and 4 o'clock - they are visible but hard to spot)
and signs of recent star formation.
This galaxy is sometimes known as M110,
although it was actually not part of
Messier's original
catalog.
APOD: April 22, 1999 - Where is Upsilon Andromedae
Explanation:
Astronomers recently announced the detection of
three large planets orbiting
the star Upsilon Andromedae - the first planetary
system known to orbit a normal
star other than our Sun.
These planets were not directly photographed but found through a Doppler
technique developed to use large telescopes to
search nearby stars
for wobbling planetary signatures.
However, Upsilon And itself is visible to the unaided eye
shining in Earth's sky in
the northern constellation Andromeda at about 4th
magnitude.
This deep photographic image shows Upsilon And
along with fainter stars and "deep sky" objects including the famous
Andromeda spiral galaxy
or M31 (right), the
Triangulum galaxy or M33
(below), and the star cluster
NGC 752 (left).
About 44 light-years distant, Upsilon And is a star only a little more
massive and just slightly hotter than the Sun.
APOD: December 4, 1998 - Centaurus A: The Galaxy Deep Inside
Explanation:
Deep inside Centaurus A, the closest
active galaxy to Earth, lies ... another galaxy!
Cen A is a giant elliptical galaxy a mere 10 million light-years
distant
with a central jumble
of stars, dust, and gas that probably hides
a massive black hole.
This composite combines an optical picture of Cen A with dark
lines tracing lobes of radio emission and an
infrared image from the
ISO satellite (in red).
The ISO data maps out the dust in what appears to be
a barred spiral galaxy
about the size of the prominent
nearby spiral M33.
The discoverers believe that the giant elliptical's gravity helps this
barred spiral galaxy maintain its shape.
In turn, material funneled along the spiral's bar fuels the central black hole
which powers the elliptical's radio lobes.
This apparently intimate association between two distinct
and dissimilar galaxies suggests a truly
cosmic symbiotic relationship.
APOD: July 21, 1998 - Nearby Spiral M33
Explanation:
M33 is a prominent nearby spiral galaxy. Nicknamed the
Triangulum,
M33
is one of the larger members of the
Local Group of Galaxies.
Two massive
spiral galaxies
dominate the Local Group:
M31 and our
Milky Way Galaxy.
M33 is the only other spiral galaxy known in the Local Group.
At 3 million light-years, M33 is the second closest spiral galaxy.
M33
is thought by some to be a satellite galaxy to massive
M31.
M33 is close enough
to appear twice the angular size of the
full moon,
when viewed with binoculars.
Globular clusters in M33's halo
appear unusual and might be much younger than
globular clusters in our
Galaxy's halo.
APOD: April 11, 1998 - NGC 604: Giant Stellar Nursery
Explanation:
Scattered within
this cavernous nebula, cataloged as NGC 604,
are over 200 newly formed hot, massive, stars.
At 1,500 light-years across, this expansive cloud of interstellar gas
and dust is effectively a giant
stellar nursery located some three million light-years distant in
the spiral galaxy, M33.
The newborn stars irradiate the gas with
energetic ultraviolet light
stripping electrons from atoms and producing a
characteristic
nebular glow.
The
details of the nebula's structure hold
clues to the mysteries of star formation and galaxy evolution.
APOD: March 14, 1998 - A Spiral Galaxy Gallery
Explanation:
A progression of beautiful spiral galaxies is illustrated above with three
photographs from NASA's Ultraviolet Imaging Telescope (UIT).
Flying above the Earth's obscuring layer of atmosphere on the
Space Shuttle Columbia during
the Astro-1 mission in 1990,
UIT's cameras were able to image these distant spirals in the ultraviolet
light produced by hot, young stars.
These bright stars, newly condensed from
gas and dust clouds, give away the location of the spiral arms
they are born in.
Because they are massive (many times the mass of the
Sun), they are shortlived.
Dying and fading before they move too far from their
birth place they make excellent tracers of spiral structure.
From left to right the galaxies are known as M33, M74, and M81 and
have progressively more tightly wound spiral arms.
Astronomers would
classify these as Scd, Sc, and Sb type spirals using a
galaxy classification scheme first worked out by
Edwin Hubble.
APOD: March 5, 1997 - In the Center of NGC 604
Explanation: Stars are sometimes born in the midst of chaos.
About 3 million years ago in the nearby galaxy M33,
a large cloud of gas spawned dense internal knots which gravitationally
collapsed to form stars. But NGC 604
was so large, it could form enough stars to make a globular cluster.
Many young stars from this cloud
are visible above, along with what is left of the initial gas
cloud. Some stars were so massive they have already evolved and
exploded in a
supernova.
The brightest stars that are left emit
light so energetic that they create one of the largest cloud of ionized hydrogen gas known,
second only to the 30 Doradus Cluster
in Milky Way's close neighbor,
the Large Magellanic Cloud.
APOD: August 16, 1996 - NGC 604: Giant Stellar Nursery in M33
Explanation:
The nebula cataloged as NGC 604 is a giant star forming region,
1500 light years across, in the nearby
spiral galaxy, M33.
Seen here in a snapshot by the Hubble Space Telescope,
over 200 newly formed,
hot, massive, stars are scattered within a cavern-like, gaseous,
interstellar cloud.
The stars irradiate the gas with energetic
ultraviolet light
stripping electrons from atoms
and exciting them - producing a characteristic
nebular glow.
The details of the nebula's structure hold clues to the mysteries of
star formation and its effect on
the evolution of galaxies.
APOD: July 13, 1996 - M81: A Bulging Spiral Galaxy
Explanation:
Few stars are still forming in the old giant spiral galaxy M81. The blue
regions
in this picture - representing
ultraviolet light -
highlight regions of bright
young stars and star formation and appear rare than in
M74 and
M33. The
red regions - representing the visible light - show a large population of
older, less massive stars.
M81
is therefore classified as
spiral galaxy
type "Sab" on the
Hubble Sequence of Galaxies. One distinguishing feature
of these types of galaxies is the relatively large central bulge
surrounding the center of the galaxy. A massive
density wave circulates
around the center of spiral galaxies. It is not well understood why the
bulge of
M81
glows as bright as it does in ultraviolet light. Speculation
includes that this may be due to hot evolved stars such as those found in
the ancient globular cluster
Omega Centauri.
APOD: July 8, 1996 - M33: The Triangulum Galaxy
Explanation:
The spiral galaxy
M33
is a mid-sized member of our
Local Group of galaxies.
M33 is also called the Triangulum Galaxy for the constellation in which it resides.
About four times smaller (in radius) than our
Milky Way Galaxy and the
Andromeda Galaxy
(M31), it is much larger than the many of the
local dwarf spheroidal
galaxies. M33's proximity to M31 causes it to be thought by some to be a
satellite galaxy of this more massive galaxy. M33's proximity to our Milky
Way galaxy causes it to appear more than twice the angular size of the
full moon, and visible with a
good pair of
binoculars.
In the
above picture, visible light is shown in red and
ultraviolet light
superposed in blue.
Stars in M33 are the most distant ever to be studied
spectroscopically.
APOD: April 9, 1996 - A Spiral Galaxy Gallery
Explanation:
A progression of beautiful spiral galaxies is illustrated above with three
photographs from NASA's Ultraviolet Imaging Telescope (UIT).
Flying above the Earth's obscuring layer of atmosphere on the
Space Shuttle Columbia during
the Astro-1 mission in 1990,
UIT's cameras were able to image these distant spirals in the ultraviolet
light produced by hot, young stars.
These bright stars, newly condensed from
gas and dust clouds, give away the location of the spiral arms
they are born in.
Because they are massive (many times the mass of the
Sun), they are shortlived.
Dying and fading before they move too far from their
birth place they make excellent tracers of spiral structure.
From left to right the galaxies are known as M33, M74, and M81 and
have progressively more tightly wound spiral arms. Astronomers would
classify these as Scd, Sc, and Sb type spirals using a
galaxy classification scheme first worked out by
Edwin Hubble.
APOD: January 8, 1996 - Local Group Galaxy NGC 205
Explanation:
The
Milky Way Galaxy is not alone. It is part of a
gathering of about 25 galaxies known as the
Local Group.
Members include the
Great Andromeda Galaxy (M31),
M32,
M33, the
Large Magellanic Clouds, the
Small Magellanic Clouds,
Dwingeloo 1, several small
irregular galaxies, and many
dwarf elliptical
galaxies. Pictured is one of the many dwarf ellipticals: NGC 205. Like
M32, NGC 205 is a companion to the large M31, and can sometimes be seen to
the south of
M31's center in
photographs. The
above image
shows this galaxy to be unusual for an
elliptical galaxy
in that it contains at least two
dust clouds (at 7 and 11
o'clock - they are visible but hard to spot) and signs of recent star
formation. This galaxy is sometimes known as M110, although it was
actually not part of
Messier's original catalog.