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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.
Fast Facts for NGC
4261: |
Credit |
X-ray: NASA/CXC/A. Zezas et
al.; Optical: Pal.Obs. DSS |
Scale |
Each panel is 237 x 290
arcsec |
Category |
Normal
Galaxies & Starburst Galaxies |
Coordinates
(J2000) |
RA 12h 19m 23.20s | Dec +05º
49' 29.60" |
Constellation |
Virgo
|
Observation
Date |
May 6, 2000 |
Observation
Time |
35 hours |
Obs.
ID |
834 |
Color
Code |
Intensity |
Instrument |
ACIS
|
Reference
|
A. Zezas, et al. NGC 4261 AND NGC 4697:
Rejuvenated Elliptical Galaxies Astrophysical Journal
Letters (in press, 2004) also astro-ph.0310567 |
Distance
Estimate |
About 100 million light
years. |
Release
Date |
December 08,
2003 | |
Chandra
Images: ' 05 |
' 04
| ' 03
| ' 02
| ' 01
| ' 00
| ' 99
| Images by
Category | |