NGC 253 Halo/ROSAT
Credit: The ROSAT Project and the Max-Planck-Institut für extraterrestrische Physik

Up the Chimney

Galaxies are dynamic places. Stellar death stirs things up as dying stars explode as supernovae, carving out huge cavities in the galaxy's gas and dust. Stellar birth can be traumatic for galaxies too. This is especially true of the so-called "starburst galaxies", in which extremely massive stars apparently are forming at an incredibly high rate. The picture above shows a ROSAT X-ray image of the starburst galaxy NGC 253. NGC 253 is a spiral galaxy (similar in shape to the Milky Way) in which the stars and gas in the galaxy are distributed in a flattened disk. The white ellipse shows the location of the disk of the galaxy. On either side of the disk are large amounts of hot, X-ray producing gas. This gas, or X-ray "halo", is thought to be produced by a strong wind from the nucleus of NGC 253. Also contributing to this emission is hot gas driven out by the hot regions of star formation, like hot air flowing up a fireplace chimney. By analyzing the X-ray emission from the halo, astronomers have shown that the "bottom" halo is pointing towards us, and the "upper" halo pointing away from us, unambiguously showing the orientation of the disk of NGC 253 in space.

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Page Author: Dr. Michael F. Corcoran
Last modified December 19, 2001