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Sagittarius A*:
Milky Way Monster Stars in Cosmic Reality Show
This Chandra image of the supermassive black hole at our Galaxy's center, a.k.a. Sagittarius A* or Sgr A*, was made from the longest X-ray exposure of that region to date. In addition to Sgr A* more than two
thousand other X-ray sources were detected in the
region, making this one of the richest fields ever
observed.
During the two-week observation period, Sgr A* flared
up in X-ray intensity half a dozen or more times. The
cause of these outbursts is not understood, but the
rapidity with which they rise and fall indicates that
they are occurring near the event horizon, or point of
no return, around the black hole. Even during the
flares the intensity of the X-ray emission from the
vicinity of the black hole is relatively weak. This
suggests that Sgr A*, weighing in at 3 million times
the mass of the Sun, is a starved black hole, possibly
because explosive events in the past have cleared much
of the gas from around it.
Evidence for such explosions was revealed in the image
- huge lobes of 20 million-degree Centigrade gas (the
red loops in the image at approximately the 2 o'clock
and 7 o'clock positions) that extend over dozens of
light years on either side of the black hole. They
indicate that enormous explosions occurred several
times over the last ten thousand years.
Further analysis of the Sgr A* image is expected to
give astronomers a much better understanding of how the
supermassive black hole in the center of our galaxy
grows and how it interacts with its environment. This
knowledge will also help to understand the origin and
evolution of even larger supermassive black holes found
in the centers of other galaxies.
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Fast Facts for
Sagittarius A*:
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Credit
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NASA/CXC/MIT/F.K.Baganoff et al.
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Scale
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Image is 8.4 arcmin on a side.
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Category
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Black
Hole
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Coordinates
(J2000)
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RA 17h 45m 40s | Dec -29º 00'
28.00" |
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Constellation
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Sagittarius
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Observation
Date
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11 pointings from September 21, 1999
through June 04, 2002
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Observation
Time
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164 hours
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Obs.
ID
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242, 1561, 2943, 3392, 3393, 3663,
3665, 2951, 2952, 2953, 2954
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Color
Code
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Energy: Red (2-3.3 keV), Green
(3.3-4.7 keV), Blue (4.7-8 keV)
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Instrument
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ACIS
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Distance
Estimate
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26,000 light years
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Release Date
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January 06, 2003
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