ACIS image of the Antennae Galaxies
Credit: X-ray (left): NASA/SAO/G.Fabbiano et al.; Optical (right): NASA/HST/Whitmore et al.

Xray image of a Cosmic Crash

The average relative distance between any two stars in a galaxy is much larger than the size of the stars themselves, meaning stellar collisions are exceedingly rare. However, the average distance between any two galaxies is not that much greater than the size of the galaxies, so that collisions between galaxies are not uncommon. A famous example of a galactic collisions is the Antennae. Now Chandra has obtained an X-ray image of the crash site. The image on the above left is a "true" color image of the Antennae by the Chandra ACIS camera, in which the color of the sources represents the energy of the x-ray emission: red represents the low energy band, green intermediate and blue the highest observed energies. The white and yellow sources are those that emit significant amounts of both low- and high-energy X-rays. The point sources are so-called "superluminous" sources, which may either be mid-mass black holes (black holes with a mass of perhaps a few hundred solar masses) or black holes whose emission is "beamed" preferentially in our direction. The image on the right is an image of the crash site from the Hubble Space Telescope. In the Hubble image most of the emission is produced by bright star forming "knots", which probably represent stellar nurseries where star formation was "triggered" by the collision. Note that, even in such galactic collisions, the chances of a collision between individual stars in the galaxies is vanishingly small.

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Page Author: Dr. Michael F. Corcoran
Last modified July 30, 2001