M87:
Giant Galaxy's Violent Past Comes Into Focus
Two Chandra observations of the giant elliptical galaxy M87 were
combined to make this long-exposure image. A central jet is surrounded
by nearby bright arcs and dark cavities in the multimillion degree
Celsius atmosphere of M87. Much further out, at a distance of about
fifty thousand light years from the galaxy's center, faint rings
can be seen and two spectacular plumes extend beyond the rings.
These features, together with radio observations, are dramatic evidence
that repetitive outbursts from the central supermassive black hole
have been affecting the entire galaxy for a hundred million years
or more. The faint horizontal streaks are instrumental artifacts
that occur for bright sources.
The accompanying closeup shows the region surrounding the jet
of high-energy particles in more detail. The jet is thought to be
pointed at a small angle to the line of sight, out of the plane
of the image. This jet may be only the latest in a series of jets
that have been produced as magnetized gas spirals in a disk toward
the supermassive black hole.
When a jet plows into the surrounding gas, a buoyant, magnetized
bubble of high-energy particles is created, and an intense sound
wave rushes ahead of the expanding bubble. These bubbles, which
rise like hot air from a fire or explosion in the atmosphere, show
up as bright regions in radio images and dark cavities in X-ray
images. Bright X-ray arcs surrounding the cavities appear to be
gas that has been swept up on rising, buoyant bubbles. An alternative
interpretation is that the arcs are shock waves that surround the
jet and are seen in projection.
A version of this long-exposure image that has been specially processed
to bring out faint features in the outer region of the galaxy reveals
two circular rings with radii of 45 thousand and 55 thousand light
years, respectively. These features are likely sound waves produced
by earlier explosions about 10 million and 14 million years ago,
respectively in M87-time (M87 is 50 million light years from Earth).
The spectacular, curved X-ray plumes extending from the upper left
to the lower right are thought to be gas carried out from the center
of the galaxy on buoyant bubbles created by previous outbursts.
A very faint arc at an even larger distance at the bottom of the
image has a probable age of 100 million years.
X-ray features similar to those seen in M87 have been observed
in other large galaxies in the centers of galaxy clusters (see,
e.g., Perseus A ). This suggests
that episodic outbursts from supermassive black holes in giant galaxies
may be common phenomena that determine how fast giant galaxies and
their central black holes grow. As gas in the galaxy cools, it would
flow inward to feed the black hole, producing an outburst which
shuts down the inflow for a few million years, at which point the
cycle would begin again.
| Fast Facts for M87:
|
|
Credit
|
NASA/CXC/W. Forman et al. |
|
Scale
|
Image is 8.6 x 13.7 arcmin |
|
Category
|
Quasars & Active Galaxies
Groups & Clusters of Galaxies |
|
Coordinates
(J2000)
|
RA 12h 30m 49.40s | Dec +12º
23' 28.00" |
|
Constellation
|
Virgo |
|
Observation
Date
|
July 29, 2000 & July 06,
2002 |
|
Observation
Time
|
118ksec |
|
Obs.
ID
|
352 (PI: Wilson), 2707 (PI: Cote) |
|
Color
Code
|
Intensity |
|
Instrument
|
ACIS
|
| References
|
W. Forman et al. Astro-ph/0312576
H. Feng et al. 2004, Astrophys. J. 607:L95-L98
A. Young et al. 2002, Astrophys. J. 579, 560 |
|
Distance Estimate
|
About 50 million light years |
| Release
Date |
May 10, 2004 |
|
|
