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Starburst Galaxies
Chandra image of M82
(NASA/CXC/SAO/PSU/CMU)
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A starburst
galaxy is a galaxy experiencing a
period of intense star forming activity. Although this activity may last for ten
million years or more, that is like a month in the life of a ten billion year old
galaxy. During a starburst, stars can form at tens, even hundreds of times
greater rates than the star formation rate in normal galaxies. Many of these
newly formed stars are very massive and very bright, so starburst galaxies are
among the most luminous galaxies.
Chandra image of NGC
253
(NASA/SAO/CXC)
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The burst occurs over a region a few thousand light years in
diameter. The most popular theory for the cause of a starburst is that it is
triggered by a close encounter or collision with another galaxy. This collision
sends shock waves rushing through the galaxy. These shock waves push on giant
clouds of gas and dust, causing them to collapse and form a few hundred stars.
The massive stars use up their fuel quickly and explode as supernovas, which produce more shock waves and more star
formation. In this way, a chain reaction of star formation and supernovas can
sweep through the central region of a galaxy, where most of the gas is located.
When most of the gas is used up or blown away by the explosions, the starburst
ends.
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