Credit: Wolfgang Pietsch

Multi-component Starburst

"Starburst galaxies" are those in which the formation of stars occurs about 100 times the rate of star formation in more normal galaxies (like the Milky Way). Starburst galaxies produce a large number of massive stars, and the galaxies can be affected by the massive stars in profound ways. Strong stellar winds and ultraviolet radiation produced by these stars disrupt and heat the gas and dust inside the galaxies. These massive stars will eventually explode as violent supernovae, doing nearly unimaginable damage and polluting the galaxy with "heavy" elements (like carbon, oxygen and the other building blocks of life). Because these processes are so energetic they produce high temperature (millions of degree) gas, and compact objects like black holes and neutron stars. Since all these objects produce X-ray radiation, X-ray observations tell quite a bit about the nature of these phenomena in starbursts. Now the XMM-Newton X-ray observatory has obtained a detailed X-ray image of a nearby starburst. This image, shown above, clearly defines different sources of X-rays in the starburst galaxy known as NGC 253. Inside the galaxy (whose size is indicated by the white ellipse), diffuse emission is seen surrounding the nucleus of the galaxy; the emission is color coded by temperature (red-green-blue for cool-warm-hot X-ray emission). A few strong X-ray point sources are clearly detected; these are probably old stars which have already collapsed to neutron stars or black holes. Analysis of this image suggests that, near the center of the galaxy (shown enlarged in the lower left corner of the image), supernova explosions occur at the outstanding rate of 1 supernova every five years (about ten-twenty times the rate of such explosions in the Milky Way)!

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