irregular galaxy

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Related to Irregular Galaxies: Elliptical Galaxies, Spiral Galaxies
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irregular galaxy
Messier 82

irregular galaxy

n.
A galaxy that does not have the clearly defined shape and structure of an elliptical, lenticular, or spiral galaxy. Irregular galaxies typically contain large amounts of gas and dust, and their stellar populations are relatively young.
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Based on its amount of hydrogen-alpha emission, a proxy for the rate of star formation, 30 Doradus ranks in the top 1% of 21,000 H II regions in 57 spiral galaxies, and it tops the 614 H II regions found in the study's 13 irregular galaxies by a factor of 10
And if we leave aside the so-called irregular galaxies, there are the lenticular galaxies, among which are the very unusual but not-so-rare spindle galaxies.
Further out are a number of similarly sized and slightly misshaped dwarf irregular galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.
Not only are these conditions typical for dwarf irregular galaxies like the SMC, they also mimic ones that would have existed in the early universe.
Irregular galaxies have no particular shape: the Small Magellanic Cloud is an example.
Modern-day galaxies come in three types: spirals with swirling, starlit arms; football-shape ellipticals; and irregular galaxies, which have no organized structure.
Unlike symmetrical spiral and elliptical galaxies, or known irregular galaxies such as the Magellanic Clouds, many of these merging pairs display strange structures such as loops, narrow streamers, and rings.
As NASA points out, spiral, elliptical and irregular galaxies can all be seen in the photo of NGC 4866.
The mix of galaxy structures in the early universe is quite different, with a much greater diversity and larger fraction of irregular galaxies, Shapley said.
NGC 2403 has two unusual neighbors--the Magellanic-type dwarf irregular galaxies Holmberg II (6.