Irregular Galaxies


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Related to Irregular Galaxies: Elliptical Galaxies, Spiral Galaxies

Irregular Galaxies

 

stellar systems that are distinguished from spiral or elliptical galaxies by their lack of orderly structure and their patchy shape. Sometimes irregular galaxies that are amorphous and have no clear form are encountered. These consist of stars and dust, whereas the majority of irregular galaxies also contain gas and a large number of very bright, hot blue giants. Clusters of the latter create the appearance of patchiness. There are irregular galaxies that have traces of spiral structure, in particular, the stellar systems closest to our galaxy, the Magellanic Clouds. Only a small number of galaxies are irregular.

References in periodicals archive ?
Previous studies have shown that the more distant dwarf irregular galaxies have large reservoirs of neutral hydrogen gas, the fuel for star formation.
The small irregular galaxies were born about 100 million years before reionization began and had just started to churn out stars.
In addition, recent work by Erik Tollerud (University of California, Irvine) and his colleagues show that the Clouds are much bluer and younger than comparably sized irregular galaxies, and they form stars at a much higher rate.
Most are spiral and irregular galaxies of normal mass, and more than 30 percent are colliding.
But they also arise in dwarf and irregular galaxies, and they surge forth in bursts of activity when galaxies collide.
Ellipticals include both the biggest and smallest galaxies in the universe, and they differ from spirals and irregular galaxies because almost all their stars are very old.
Nothing in my notes, however, suggests that one of these irregular galaxies is more difficult to observe than the other, so the selection must have been arbitrary.
The Magellanic-type irregular galaxies are defined as having no nucleus at all: whereas ellipticals are "all bulge," Magellanic irregulars are "all disk.
It is nearly invisible in the elliptical galaxies that have only old stars but practically all you see in irregular galaxies like the Magellanic Clouds.
Type Ib, Ic, and II supernovae are always found in spiral or irregular galaxies, usually in spiral arms and near ionized-hydrogen (H II) regions, sites of active star formation.