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NGC 4261:
Trail of Black Holes and Neutron Stars Points to Ancient Collision
The Chandra image of the elliptical galaxy
NGC 4261 reveals dozens of black holes and neutron stars strung out
across tens of thousands of light years like beads on a necklace.
The spectacular structure, which is not apparent from the optical
image of the galaxy, is thought to be the remains of a collision between
galaxies a few billion years ago.
According to this interpretation,
a smaller galaxy was captured and pulled apart by the gravitational
tidal forces of NGC 4261. As the doomed galaxy fell into the larger
galaxy, large streams of gas were pulled out into long tidal tails.
Shock waves in these tidal tails triggered the formation of many massive
stars.
Over the course of a few million years, these stars evolved
into neutron stars or black holes. A few of these collapsed stars
had companion stars, and became bright X-ray sources as gas from the
companions was captured by their intense gravitational fields.
The
currently favored view is that elliptical galaxies are produced by
collisions between spiral galaxies. Computer simulations of galaxy
collisions support this idea, and optical evidence of tails, shells,
ripples, arcs and other structures have been interpreted as evidence
for this theory.
However as the image shows, the optical evidence rather quickly fades
into the starry background of the galaxy, whereas the X-ray signature
lingers for hundreds of millions of years. Chandra's image of NGC
4261 shows that X-ray observations may be the best way to identify
the ancient remains of mergers between galaxies.
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Fast Facts for
NGC 4261:
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Credit
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X-ray: NASA/CXC/A. Zezas et
al.; Optical: Pal.Obs. DSS |
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Scale
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Each panel is 237 x 290 arcsec |
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Category
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Normal
Galaxies & Starburst Galaxies |
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Coordinates
(J2000)
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RA 12h 19m 23.20s | Dec +05º
49' 29.60" |
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Constellation
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Virgo |
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Observation
Date
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May 6, 2000 |
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Observation
Time
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35 hours |
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Obs.
ID
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834 |
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Color
Code
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Intensity |
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Instrument
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ACIS
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Reference
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A. Zezas, et al. NGC 4261 AND NGC 4697: Rejuvenated Elliptical Galaxies Astrophysical Journal Letters (in press, 2004) also astro-ph.0310567 |
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Distance Estimate
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About 100 million light years. |
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Release Date
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December 08, 2003 |
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