starburst galaxy(redirected from Star burst galaxies)
starburst galaxyA galaxy in which a massive burst of star formation is currently taking place: it is characterized by an infrared luminosity that is considerably larger than its optical luminosity, sometimes by a factor of 50 or more. The luminosity of starburst galaxies can compare to the bolometric luminosity of quasars, but is powered by a fundamentally different mechanism. The starburst occurs in a region over a kiloparsec in size, thus distinguishing these galaxies from active galaxies, which have a tiny central powerhouse. A few nearby starburst galaxies (e.g. M82) have long been known from their disturbed optical appearance, but their widespread occurrence was only established when thousands were revealed by infrared satellite IRAS. They are basically spirals in which the star formation is proceeding at a rate that cannot be sustained for much of the lifetime of the galaxy. The trigger for the burst of star formation is unclear although in some cases the gravitational effect of a companion galaxy may be responsible (see interacting galaxies). The new stars are still enveloped in the galaxy's dense molecular clouds; their ultraviolet radiation is absorbed by dust in the clouds and reradiated as infrared. See also IRAS galaxies.
starburst galaxy[′stär‚bərst ‚gal·ik·sē]
A galaxy that is presently undergoing a period of intense star formation.