Arp 220/Chandra
Credit: NASA/SAO/CXC/J.McDowell

Not Just Passing Through

Galaxies are largely empty space. When two galaxies collide, there's little chance that individual stars in each galaxy will crash into each other. That doesn't mean that galaxy-galaxy collisions are not accompanied with their own fireworks, however. The image above shows an X-ray image, obtained by the Chandra X-ray observatory, of a pair of colliding galaxies known as Arp 220. This image shows a bright central region at the waist of a glowing hour-glass-shaped cloud of multimillion degree gas that is rushing out of the galaxy at hundreds of thousands of miles per hour. Astronomers believe this emission is produced by a "superwind" generated by hundreds of millions of newly-formed stars, perhaps triggered by the collision. Farther out, Chandra sees giant giant lobes of hot gas, possibly thrown out by the impact of the collision, and which possibly may escape the galaxies entirely. Chandra also detects 2 bright pin-points of X-ray emission, possibly arising near supermassive black holes in the galactic nuclei. If so, the two black holes may eventually merge, producing their own fireworks (including gravitational fireworks) - but this won't happen for hundreds of millions of years.

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Page Author: Dr. Michael F. Corcoran
Last modified May 6, 2002