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Astronomy Picture of the Day |
APOD: 2025 April 17 - Virgo Cluster Galaxies
Explanation:
Galaxies of the Virgo Cluster
are scattered across this nearly 4 degree wide
telescopic field of view.
About 50 million light-years distant, the
Virgo Cluster
is the closest large galaxy cluster to our own local galaxy group.
Prominent here are Virgo's bright elliptical galaxies from the
Messier
catalog,
M87 at bottom left, and M86 and M84 near center right.
M86 and M84 are recognized as part of
Markarian's Chain,
the visually striking line-up of galaxies on the
that runs through the upper portion of this frame.
Near the middle of the chain lies an intriguing interacting pair of
galaxies, NGC 4438 and NGC 4435,
known to some as Markarian's Eyes.
Still,
giant elliptical galaxy M87
dominates the Virgo cluster.
It's the home of a super massive black hole,
the first black hole ever imaged by planet Earth's
Event Horizon
Telescope.
APOD: 2025 February 20 - Messier 87
Explanation:
Enormous elliptical galaxy
Messier 87
is about 50 million light-years away.
Also known as NGC 4486, the giant galaxy holds
trillions of stars compared to the mere billions of stars in our
large spiral Milky Way.
M87 reigns as the large central elliptical galaxy in the
Virgo galaxy cluster.
An energetic jet from the giant galaxy's core
is seen to stretch outward for about 5,000 light-years
in this sharp optical and near-infrared
view from the Hubble
Space Telescope.
In fact, the cosmic blow torch is seen across the electromagnetic spectrum from
gamma-rays to radio wavelengths.
Its ultimate power source
is M87's central, supermassive black hole.
An image of this monster in the middle of M87 has been captured by
planet Earth's
Event Horizon Telescope.
APOD: 2024 May 9 - The Galaxy, the Jet, and a Famous Black Hole
Explanation:
Bright elliptical galaxy Messier 87 (M87)
is home to the
supermassive black hole captured in 2017 by planet Earth's
Event Horizon Telescope
in the first ever image of a black hole.
Giant of the Virgo galaxy cluster about 55 million light-years away,
M87 is rendered in blue hues in this infrared
image from the Spitzer Space telescope.
Though M87 appears mostly featureless and cloud-like,
the Spitzer image does record details of relativistic
jets blasting from the galaxy's central region.
Shown in the inset at top right, the jets themselves
span thousands of light-years.
The brighter jet seen on the
right is approaching and close to our line of sight.
Opposite, the shock created by the otherwise unseen receding jet
lights up a fainter arc of material.
Inset at bottom right, the
historic black hole image is shown
in context at the center of giant galaxy, between the relativistic jets.
Completely unresolved in the Spitzer image, the
supermassive
black hole surrounded by infalling material is the source of enormous
energy driving
the relativistic jets from the center of active galaxy M87.
The Event Horizon Telescope image of M87
has been enhanced to reveal a
sharper view of
the famous supermassive black hole.
APOD: 2024 April 1 – Swirling Magnetic Field around Our Galaxy's Central Black Hole
Explanation:
What's happening to the big black hole in the center of our galaxy?
It is sucking in matter from a swirling disk -- a disk that is
magnetized, it has now been confirmed.
Specifically, the
black hole's accretion disk
has recently been seen to emit
polarized light,
radiation frequently associated with a
magnetized source.
Pictured here is a close-up of Sgr A*, our
Galaxy's central black hole, taken by
radio telescopes
around the world participating in the
Event Horizon Telescope (EHT) Collaboration.
Superposed are illustrative curved lines indicating
polarized light likely emitted from
swirling magnetized gas that will soon fall into the
4+ million solar mass
central black hole.
The central part of this image is likely dark because little light-emitting gas is visible between us and the
dark event
horizon of the black hole.
Continued EHT monitoring of this and M87's central black hole may
yield new clues
about the gravity of black holes and how infalling matter creates
disks and
jets.
APOD: 2023 May 26 - Virgo Cluster Galaxies
Explanation:
Galaxies of the Virgo Cluster
are scattered across this nearly 4 degree wide
telescopic field of view.
About 50 million light-years distant, the Virgo Cluster is the
closest large galaxy cluster to our own local galaxy group.
Prominent here are Virgo's bright elliptical galaxies
Messier catalog,
M87 at bottom center, and M84 and M86 (top to bottom)
near top left.
M84 and M86 are recognized as part of
Markarian's Chain,
a visually striking line-up of galaxies on the
left side of this frame.
Near the middle of the chain lies an intriguing interacting pair of galaxies,
NGC 4438 and NGC 4435,
known to some as Markarian's Eyes.
Of course
giant elliptical galaxy M87
dominates the Virgo cluster.
It's the home of a super massive black hole,
the first black hole ever imaged by planet Earth's
Event Horizon Telescope.
APOD: 2023 May 4 - The Galaxy, the Jet, and a Famous Black Hole
Explanation:
Bright elliptical galaxy Messier 87 (M87)
is home to the
supermassive black hole captured in 2017 by planet Earth's
Event Horizon Telescope
in the first ever image of a black hole.
Giant of the Virgo galaxy cluster about 55 million light-years away,
M87 is the large galaxy rendered in blue hues in this infrared
image
from the Spitzer Space telescope.
Though M87 appears mostly featureless and cloud-like,
the Spitzer image does record details of relativistic
jets blasting from the galaxy's central region.
Shown in the inset at top right, the jets themselves
span thousands of light-years.
The brighter jet seen on the
right is approaching and close to our line of sight.
Opposite, the shock created by the otherwise unseen receding jet
lights up a fainter arc of material.
Inset at bottom right, the
historic black hole image is shown
in context, at the center of giant galaxy and relativistic jets.
Completely unresolved in the Spitzer image, the
supermassive
black hole surrounded by infalling material is the source of enormous energy driving
the
relativistic jets from the center of active galaxy M87.
The Event Horizon Telescope image of M87
has now been enhanced to reveal a
sharper view of the famous supermassive black hole.
APOD: 2022 May 1 - First Horizon Scale Image of a Black Hole
Explanation:
What does a black hole look like?
To find out,
radio telescopes from around the Earth coordinated observations of
black holes with the largest known
event horizons on the sky.
Alone, black holes are just
black,
but these monster attractors are known to be surrounded by glowing gas.
This first image
resolves the area around the
black hole at the center of
galaxy M87
on a scale below that expected for its
event horizon.
Pictured, the dark central region is not the event horizon, but rather the
black hole's shadow -- the central region of
emitting gas darkened by the central black hole's gravity.
The size and shape of the shadow is determined by bright gas
near the event horizon,
by strong
gravitational lensing deflections, and by the black hole's spin.
In resolving
this black hole's shadow, the
Event Horizon Telescope
(EHT) bolstered evidence that
Einstein's gravity works even in
extreme regions, and gave clear evidence that
M87
has a central spinning black hole of about 6 billion solar masses.
Since releasing this featured image in 2019, the
EHT has expanded to
include more telescopes,
observe more black holes, track
polarized light,and is working to observe
the immediately vicinity of the
black hole in
the center of our
Milky Way Galaxy.
APOD: 2021 April 15 - The Galaxy, the Jet, and a Famous Black Hole
Explanation:
Bright elliptical galaxy Messier 87 (M87)
is home to the
supermassive black hole captured by planet Earth's
Event Horizon Telescope
in the first ever image of a black hole.
Giant of the Virgo galaxy cluster about 55 million light-years away,
M87 is the large galaxy rendered in blue hues in this infrared
image from the Spitzer Space telescope.
Though M87 appears mostly featureless and cloud-like,
the Spitzer image does record details of relativistic
jets blasting from the galaxy's central region.
Shown in the inset at top right, the jets themselves
span thousands of light-years.
The brighter jet seen on the
right is approaching and close to our line of sight.
Opposite, the shock created by the otherwise unseen receding jet
lights up a fainter arc of material.
Inset at bottom right, the
historic black hole image is shown
in context, at the center of giant galaxy and relativistic jets.
Completely unresolved in the Spitzer image, the supermassive
black hole surrounded by infalling material is the source of
enormous energy driving
the relativistic jets from the center of active galaxy M87.
APOD: 2021 March 31 - M87's Central Black Hole in Polarized Light
Explanation:
To play on
Carl Sagan’s
famous words
"If you wish to make black hole jets, you must first create magnetic fields."
The featured image represents the
detected intrinsic spin direction
(polarization) of
radio waves.
The polarizationi is produced by the powerful
magnetic field
surrounding the supermassive black hole at the center of
elliptical galaxy
M87.
The radio waves were detected by the
Event Horizon Telescope (EHT),
which combines data from radio telescopes distributed worldwide.
The
polarization structure, mapped using computer generated
flow lines,
is overlaid on
EHT’s famous black hole image, first published in 2019.
The full 3-D magnetic field is
complex.
Preliminary
analyses indicate that parts of the field circle around the
black hole along with the
accreting matter, as expected.
However,
another component seemingly veers vertically away from the black hole.
This component could
explain how
matter resists falling in and is instead launched into
M87’s jet.
APOD: 2020 October 10 - Virgo Cluster Galaxies
Explanation:
Galaxies of the Virgo Cluster
are scattered across this deep telescopic field of view.
The cosmic scene spans about three Full Moons, captured in dark skies near
Jalisco, Mexico, planet Earth.
About 50 million light-years distant, the Virgo Cluster is the
closest large galaxy cluster to our own local galaxy group.
Prominent here are Virgo's bright elliptical galaxies from the
Messier catalog,
M87 at the top left, and M84 and M86 seen
(bottom to top) below and right of center.
M84 and M86 are recognized as part of
Markarian's Chain,
a visually striking line-up of galaxies vertically on the
right side of this frame.
Near the middle of the chain lies an intriguing interacting pair of galaxies,
NGC 4438 and NGC 4435,
known to some as Markarian's Eyes.
Of course
giant elliptical galaxy M87
dominates the Virgo cluster.
It's the home of a super massive black hole,
the first black hole ever imaged by planet Earth's
Event Horizon Telescope.
APOD: 2019 April 27 - The Galaxy, the Jet and the Black Hole
Explanation:
Bright elliptical galaxy
Messier 87 (M87) is home to the
supermassive black hole captured by planet Earth's
Event Horizon Telescope
in the first ever image of a black hole.
Giant of the Virgo galaxy cluster about 55 million light-years away,
M87 is the large galaxy rendered in blue hues in this infrared
image
from the Spitzer Space telescope.
Though M87 appears mostly featureless and cloud-like,
the Spitzer image does record details of relativistic
jets blasting from the galaxy's central region.
Shown in the inset at top right, the jets themselves
span thousands of light-years.
The brighter jet seen on the
right is approaching and close to our line of sight.
Opposite, the shock created by the otherwise unseen receding jet
lights up a fainter arc of material.
Inset at bottom right, the
historic black hole image is shown
in context, at the center of giant galaxy and relativistic jets.
Completely unresolved in the Spitzer image, the supermassive
black hole surrounded by infalling material is the source of the
enormous energy driving the relativistic jets from the
center
of active galaxy M87.
APOD: 2019 April 11 - First Horizon Scale Image of a Black Hole
Explanation:
What does a black hole look like?
To find out,
radio telescopes from
around the Earth coordinated observations of
black holes with the largest known
event horizons on the sky.
Alone, black holes are just
black,
but these monster attractors are known to be surrounded by glowing gas.
The first image was released yesterday and
resolved the area around the
black hole at the center of
galaxy M87
on a scale below that expected for its
event horizon.
Pictured, the dark central region is not the event horizon, but rather the
black hole's shadow -- the central region of
emitting gas darkened by the central black hole's gravity.
The size and shape of the shadow is determined by bright gas
near the event horizon,
by strong
gravitational lensing deflections, and by the black hole's spin.
In resolving
this black hole's shadow, the
Event Horizon Telescope
(EHT) bolstered evidence that
Einstein's gravity works even in
extreme regions,
and gave clear evidence that
M87
has a central spinning black hole of about 6 billion solar masses.
The EHT is not done -- future observations will be geared toward even higher resolution,
better tracking of variability, and exploring the immediate vicinity of the
black hole in
the center of our
Milky Way Galaxy.
APOD: 2017 June 24 - Markarian's Chain to Messier 64
Explanation:
Top to bottom,
this colorful and broad telescopic mosaic links
Markarian's Chain
of galaxies across the core of the Virgo Cluster to
dusty spiral galaxy Messier 64.
Galaxies are scattered through the field of view that spans some 20 full
moons across a gorgeous night sky.
The cosmic frame is also filled with foreground stars from
constellations Virgo and the well-groomed Coma Berenices, and
faint, dusty nebulae drifting above the plane of the Milky Way.
Look carefully for
Markarian's eyes.
The famous pair of interacting galaxies is near the top, not far
from M87,
the Virgo cluster's giant elliptical galaxy.
At the bottom, you can stare down
Messier 64, also known as the
Black Eye Galaxy.
The Virgo Cluster is the closest large galaxy cluster to our own
local
galaxy group.
Virgo
Cluster galaxies are about 50 million light-years distant,
but M64 lies a mere 17 million light-years away.
APOD: 2015 August 4 - Virgo Cluster Galaxies
Explanation:
Well over a thousand galaxies are known members of
the Virgo Cluster,
the closest large cluster of galaxies to our own
local group.
In fact, the galaxy cluster is difficult
to
appreciate all at once because
it covers such a large area on the sky.
This careful wide-field
mosaic of telescopic images
clearly records the central region of the Virgo Cluster through faint
foreground dust
clouds lingering above the plane of our own Milky Way galaxy.
The cluster's dominant giant elliptical
galaxy M87, is just below and to the left of the frame center.
To the right of M87 is a string of galaxies known as
Markarian's Chain.
A closer examination of the image will
reveal many Virgo cluster member
galaxies as small fuzzy patches.
Sliding your cursor over the image will label the larger galaxies
using NGC catalog designations.
Galaxies are also shown with
Messier
catalog numbers, including
M84, M86,
and prominent colorful spirals
M88,
M90, and
M91.
On average, Virgo Cluster galaxies are measured to be
about 48 million light-years away.
The Virgo
Cluster distance has been used to give an important
determination of the Hubble Constant and
the scale of the Universe.
APOD: 2011 August 28 - A Jet from Galaxy M87
Explanation:
What's causing a huge jet to emanate from the center of galaxy
M87?
Although the
unusual jet was first noticed early in the
twentieth century,
the exact cause is still debated.
The above picture taken by the
Hubble Space Telescope in 1998 shows clear details, however.
The most
popular hypothesis holds that the
jet is created
by energetic gas swirling around a massive
black hole at the galaxy's center.
The result is a 5000
light-year long
blowtorch where
electrons are ejected outward at near light-speed,
emitting eerily blue light during a magnetic spiral.
M87 is a giant
elliptical galaxy
residing only 50 million light-years away in the
Virgo Cluster of Galaxies.
The faint dots of light
surrounding
M87's center are large ancient
globular clusters of stars.
APOD: 2011 April 22 - Virgo Cluster Galaxies
Explanation:
Well over a thousand galaxies are known members of
the Virgo
Cluster,
the closest large cluster of galaxies to our own
local group.
In fact, the galaxy cluster is difficult
to
appreciate all at once because
it covers such a large area on the sky.
Spanning about 5x3 degrees, this careful
mosaic of telescopic images
clearly records the central
region of the Virgo Cluster through faint
foreground dust
clouds lingering above the plane of our own Milky Way galaxy.
The cluster's dominant giant elliptical
galaxy M87, is just below center in the frame.
Above M87 is the famous interacting galaxy pair NGC 4438,
also known as The Eyes.
A closer examination of the image will
reveal many Virgo cluster member galaxies as small fuzzy patches.
Sliding your cursor over the image will label the larger galaxies
using NGC catalog designations.
Galaxies are also shown with
Messier
catalog numbers, including
M84, M86,
and prominent colorful spirals
M88,
M90, and M91.
On average, Virgo Cluster galaxies are measured to be
about 48 million light-years away.
The Virgo
Cluster distance has been used to give an important
determination of the Hubble Constant and
the scale of the Universe.
(Editor's Note: Labels courtesy of
Astrometry.net.)
APOD: 2010 May 20 - M87: Elliptical Galaxy with Jet
Explanation:
In spiral galaxies, majestic
winding arms
of young stars, gas, and dust rotate in a flat disk around a
bulging galactic nucleus.
But elliptical galaxies seem to be simpler.
Lacking gas and dust to form new stars, their
randomly swarming older stars, give them an ellipsoidal
(egg-like) shape.
Still, elliptical galaxies can be very large.
Centered in
this
telescopic view and over 120,000 light-years in
diameter, larger than our own Milky Way,
elliptical galaxy M87
(NGC 4486) is the dominant galaxy of the
Virgo
Galaxy Cluster.
Some 50 million light-years away,
M87 is
likely home to a supermassive
black hole responsible
for a high-energy jet of particles emerging from the giant
galaxy's central region.
In this well-processed image, M87's jet is
near
the one o'clock position.
Other galaxies are also in the field of view,
including large Virgo Cluster ellipticals
NGC 4478
right of center and
NGC 4476
near the right edge.
APOD: 2006 May 20 - Elliptical Galaxy M87
Explanation:
In spiral galaxies, majestic
winding arms of young stars and
interstellar gas and dust rotate in a flat disk around a
bulging galactic nucleus.
But elliptical galaxies seem to be simpler.
Lacking gas and dust to form new stars, their
randomly swarming older stars, give them an ellipsoidal
(egg-like) shape.
Still, elliptical galaxies can be very large.
Over 120,000 light-years in diameter (larger than our own
Milky Way), elliptical galaxy M87 is the dominant
galaxy at the center
of the Virgo Galaxy Cluster, some 50 million light-years away.
M87 is likely home to a supermassive
black hole responsible
for the high-energy jet of particles emerging from the giant
galaxy's central region.
APOD: 2005 March 16 - Markarian's Chain of Galaxies
Explanation:
Across the heart of the
Virgo Cluster of Galaxies
lies a striking string of galaxies known as Markarian's Chain.
The chain,
pictured above, is highlighted on the upper right with
two large but featureless
lenticular galaxies,
M84 and
M86,
and connects to the large
spiral on the lower left,
M88.
Prominent on the lower right but not part of
Markarian's Chain is the giant
elliptical galaxy
M87.
The home Virgo Cluster is the nearest
cluster of galaxies, contains over 2000 galaxies,
and has a noticeable gravitational pull on the galaxies of the
Local Group of Galaxies surrounding our
Milky Way Galaxy.
The center of the
Virgo Cluster is located about 70 million
light years away toward the constellation of Virgo.
At least seven galaxies in
the chain
appear to move coherently,
although others appear to be superposed by chance.
APOD: 2004 December 11 - M87's Energetic Jet
Explanation:
An
energetic jet from the core of
giant elliptical galaxy M87 stretches outward for 5,000 light-years.
This monstrous jet
appears
in the panels above
to be a knotted and irregular structure, detected
across the spectrum, from
x-ray to optical to
radio wavelengths.
In all these bands,
the observed emission is likely created as high energy
electrons spiral along magnetic field lines, so called
synchrotron radiation.
But what powers this cosmic blowtorch?
Ultimately, the jet is thought to be produced
as matter near the center of M87
swirls toward a spinning, supermassive black hole.
Strong electromagnetic forces are generated and eject material
away from
the black hole along
the axis of rotation in a narrow jet.
Galaxy M87
is about 50 million light-years away and reigns as
the large central elliptical galaxy in the
Virgo
cluster.
APOD: 2004 June 16 - Elliptical Galaxy M87
Explanation:
Elliptical galaxy
M87 is a type of
galaxy that looks much different than our own
Milky Way Galaxy.
Even for an
elliptical galaxy,
though, M87 is peculiar.
M87 is much bigger than an average galaxy, appears near the
center of a whole
cluster of galaxies known as the
Virgo Cluster,
and shows an unusually high number of globular clusters.
These globular clusters
are visible as faint spots surrounding the bright center of
M87.
In general,
elliptical galaxies contain similar numbers of stars as
spiral galaxies, but are ellipsoidal in shape (spirals are mostly flat), have no spiral structure, and little
gas and
dust.
The
above image of M87 was taken recently by the
Canada-France-Hawaii
Telescope
on top of the dormant volcano
Mauna Kea in
Hawaii,
USA.
APOD: 2001 November 1 - M87's Energetic Jet
Explanation:
An
energetic jet from the core of
giant elliptical galaxy M87 stretches outward for 5,000 light-years.
This monstrous jet
appears
in the panels above
to be a knotted and irregular structure, dectected
across the spectrum, from
x-ray to optical to
radio wavelengths.
In all these bands,
the observed emission is likely created as high energy
electrons spiral along magnetic field lines, so called
synchrotron radiation.
But what powers this cosmic blowtorch?
Ultimately, the jet is thought to be produced
as matter near the center of M87
swirls toward a spinning, supermassive black hole.
Strong electromagnetic forces are generated and eject material
away from
the black hole along
the axis of rotation in a narrow jet.
Galaxy M87
is about 50 million light-years away and reigns as
the large central elliptical galaxy in the
Virgo
cluster.
APOD: 2001 January 26 - Galaxies Of The Virgo Cluster
Explanation:
Well over a thousand galaxies are known members of
the Virgo Cluster,
the closest large cluster of galaxies to our own
local group.
The galaxy cluster is difficult
to see
all at once because
it covers such a large area
on the sky.
Still,
this excellent
telescopic view records the region of the
Virgo Cluster around its dominant giant elliptical
galaxy M87.
M87 can be seen as a fuzzy patch near the picture's bottom center.
In fact, a close examination of the image will
reveal that many of the "stars" are
actually surrounded by a telltale fuzz, indicating
that they are
Virgo Cluster galaxies.
How many galaxies can you pick out?
Click on the image for an uncropped, labeled version which includes the
NGC catalog
numbers for most of the visible galaxies.
On average,
Virgo Cluster galaxies are measured to be
about 48 million light-years away.
The Virgo
Cluster distance has been used to give an important
determination of the Hubble Constant and
the scale of the Universe.
APOD: 2000 July 6 - A Jet from Galaxy M87
Explanation:
What's causing a huge jet to emanate from the center of galaxy
M87?
Although the
unusual jet was first noticed early in the
twentieth century,
the exact cause is still debated.
The above recently released picture taken by the
Hubble Space Telescope
shows clear details, however.
The most
popular hypothesis holds that the
jet is created
by energetic gas swirling around a massive
black hole at the galaxy's center.
The result is a 5000
light-year long blowtorch where
electrons are ejected outward at near light-speed,
emitting eerily blue light during a magnetic spiral.
M87 is a giant
elliptical galaxy
residing only 50 million light-years away in the
Virgo Cluster of Galaxies.
The faint dots of light surrounding
M87's center are large ancient
globular clusters of stars.
APOD: 2000 February 20 - The Virgo Cluster of Galaxies
Explanation:
Pictured are several galaxies of the Virgo Cluster,
the closest
cluster of galaxies to our
Milky Way Galaxy.
The
Virgo Cluster spans more than 5 degrees on the sky -
about 10 times the angle made by a
full Moon.
It contains over 100 galaxies of many types - including
spirals,
ellipticals, and
irregular
galaxies.
The
Virgo Cluster is so massive that it is noticeably
pulling our Galaxy toward it.
The cluster contains not only galaxies filled with stars but also
gas so hot it glows in
X-rays.
Motions of galaxies in and around clusters indicate
that they contain more
dark matter than any visible matter we can see.
Notable bright galaxies in the Virgo Cluster include
bright Messier objects such as
M61,
M87,
M90, and
M100.
APOD: February 16, 1999 - The Large and Small of M87
Explanation:
The small core of
elliptical galaxy M87
appears to be energizing its whole galactic neighborhood.
Recent images from the
Very Large Array (VLA) of
radio telescopes indicate that huge bubbles of
hot gas not only exist but are still being created.
These bubbles measure 200,000 light-years across
and surround the
entire galaxy.
The source creating and feeding the bubbles
has been traced to jets pointing back to
M87's center, where a
supermassive black hole
is thought to live. The smallest scale on the
above radio-map is 0.2 light-years and imaged by
many radio telescopes working together (VLBI).
The labeled numbers
refer to the wavelength of the radio waves observed.
The exact composition of these jets is not known, but thought to contain various
subatomic particles.
APOD: April 5, 1997 - A Black Hole in M87?
Explanation:
The center of nearby giant galaxy
M87 is a dense and violent place. In
this
1994 photograph by the
Hubble Space Telescope, a disk of hot
gas was found to be orbiting at the center of this massive
elliptical galaxy. The
disk is evident at the lower left of the picture. The rotation
speed of gas in this disk indicates the mass of the object the gas is
orbiting, while the size of the disk indicates an approximate volume of the
central object.
These observations
yield a central density so high that the
only hypothesized object that could live there is a
black hole. The
picture also shows a highly
energetic jet emanating from the central
object like a cosmic blowtorch.
The jet is composed of fast moving charged particles and has
broken into knots as small as 10 light years across.
APOD: April 19, 1996 - The Virgo Cluster: Hot Plasma and Dark Matter
Explanation:
This ROSAT image of the
Virgo cluster of galaxies reveals a
hot X-ray emitting plasma or gas with a
temperature of 10-100 million degrees pervading
the cluster. False colors have been used to represent
the intensity of X-ray emission.
The large area of X-ray emission, just below and left of center,
is about 1 million light-years across.
The giant elliptical galaxy M87,
the biggest member
of the cluster, is centered in that area while
other cluster members
are scattered around it.
By adding up the amount of
X-ray emitting gas astronomers
have found that its total mass is
up to 5 times the total mass of the cluster galaxies themselves -
yet all this
matter still does not produce nearly enough gravity to keep
the cluster from flying apart! Where is the unseen mass?
Because galaxy clusters are the
largest structures in the Universe, this
mysterious Dark Matter must dominate the cosmos
but its nature is still an
open question.
APOD: March 5, 1996 - A Black Hole in M87's Center?
Explanation:
The center of nearby giant galaxy
M87 is a dense and violent place. In
this
1994 photograph by the
Hubble Space Telescope, a disk of hot
gas was
found to be orbiting at the center of this massive
elliptical galaxy. The
disk is evident on the lower left of the above photograph. The rotation
speed of gas in this disk indicates the mass of the object the gas is
orbiting, while the size of the disk indicates an approximate volume of the
central object.
These observations yield a central density so high that the
only hypothesized object that could live there is a
black hole. The
picture also shows a highly energetic
jet emanating from the central
object. The jet is composed of fast moving charged particles and has
broken into knots as small as 10 light years across.
APOD: September 13, 1995 - Elliptical Galaxy M87
Explanation:
Elliptical galaxy M87 is a type of
galaxy that looks much different
than our own
Milky Way Galaxy. But even for an
elliptical galaxy M87 is peculiar.
M87 is much bigger than an average
galaxy, appears at the center of a whole cluster of galaxies known as the
Virgo Cluster, and shows a very high number of
globular clusters.
These globular clusters are visible as faint
spots surrounding the bright center of M87. In general, elliptical galaxies
contain similar numbers of stars as
spiral galaxies, but are ellipsoidal in
shape (spirals are mostly flat), have no spiral structure, and little
gas and
dust.
This picture is number sixty on a publicly posted list of
images from the
Anglo-Australian
Telescope (AAT).