Chandra and optical composite image of NGC 1232
Credit: X-ray: NASA/CXC/Huntingdon Inst. for X-ray Astronomy/G.Garmire, Optical: ESO/VLT

Pointing to a Cosmic Collision

How often do collisions between galaxies occur on the cosmic superhighway? Sometimes these collisions are caught in the act and can be easily recognized, but even normal-looking galaxies can hide a violent past. The image above shows a composite of optical and X-ray images of a galaxy known as NGC 1232, a rather unassuming spiral galaxy when seen in visual light. But if you use the X-ray vision of the Chandra X-ray Observatory, a comet-shaped cloud of glowing, 6 million degree gas comes into view. This cloud is seen as the purple emission region in the image above. The shape and location of this hot gas is unusual; astronomers think that this cloud is probably the remnant of an energetic collision between NGC 1232 and a smaller dwarf galaxy. If this is correct, then apparently NGC 1232 completely swallowed the dwarf galaxy and its stars. But the violent collision would have produced the superheated cloud of gas visible to Chandra, and may have helped trigger the formation of a cluster of massive stars.
Published: August 26, 2013

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Page Author: Dr. Michael F. Corcoran
Last modified Sunday, 29-Dec-2013 21:30:27 EST