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NGC 1637:
What Lies Beneath
A series of Chandra observations of the spiral
galaxy NGC 1637 has provided a dramatic view of a violent, restless
nature that belies its serene optical image. Over a span of
21 months, intense neutron star and black hole X-ray sources flashed
on and off, giving the galaxy the appearance of a cosmic Christmas
tree.
Erratic, volatile behavior is a common characteristic of neutron stars
or black holes with orbiting normal companion stars. Gas ripped off
the normal star falls toward the compact star where the gas is compressed
and heated by gravitational fields billions of times stronger than
on the surface of the Sun. This process generates powerful X-radiation
that can flare up and subside in a matter of seconds.
The X-ray view is in marked contrast to the view with an optical telescope.
Optically, the galaxy is a stately spiral lit by the glow of about
fifty billion stars slowly evolving over millions and billions of
years.
This tranquil scene is interrupted about once a century with a supernova
that signals the death of a star, and in many cases the formation
of a neutron star or black hole. It was the detection of such a supernova
in 1999 that triggered the subsequent series of Chandra observations.
The supernova appears in the panels on days 4 and 49 as the faint
source at the five o’clock position just below the diffuse glow in
the center of the image. The supernova faded in a few months, but
the Chandra observations continued on five more occasions in coordination
with the Hubble Space Telescope and the Very Large Array radio telescope.
This collaboration produced a valuable data set of long term radio,
optical and X-ray observations of the galaxy.
Of particular note is an extremely bright (white) X-ray source that
appears in all panels at the nine o’clock position. This source is
located in a group of massive stars in one of the outer spiral arms
of the galaxy. It is likely a black hole formed relatively recently
(in the last million years or so) when a massive star exhausted its
nuclear fuel, exploded as a supernova and left behind a black hole
which is now pulling in gas from a companion star.
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Fast Facts for
NGC 1637:
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Credit
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NASA/CXC/Penn State/S. Immler
et al. |
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Scale
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Each panel is 8.5 arcmin per
side |
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Category
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Normal
Galaxies & Starburst Galaxies |
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Coordinates
(J2000)
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RA 04h 41m 27.10s | Dec -02º
51' 45.70" |
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Constellation
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Andromeda |
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Observation
Date
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1999: Nov 1, Nov 13, Dec 16;
2000: Feb 7, Oct 30; 2001: Mar 6, Jul 22 |
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Observation
Time
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168.1 ksec |
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Obs.
ID
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763-766, 1968-1970 |
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Color
Code
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Energy (Red 0.3-1.5 keV, Green
1.5-3.0 keV, Blue 3.0-7.0 keV) |
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Instrument
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ACIS
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Reference
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S. Immler et al. Ap. J. 595, 727 (2003
October 1) "A Deep Chandra X-ray Observation of NGC
1637" |
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Distance Estimate
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About 38 million light years |
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Release Date
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October 28, 2003 |
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