Astronomy: Irregular Galaxies

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Source: Wikipedia (CC BY-SA)

Irregular Galaxies Irregular galaxy is a galaxy that does not have a distinct regular shape, un like a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure. Other galaxies have an axis of symmetry for their blue-light distribution, which cannot be found in the sporadic organization of irregular galaxies.

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Why Irregular Galaxies matters: Galaxies are the fundamental building blocks of the visible universe. Studying them reveals how matter organized itself after the Big Bang and continues to evolve billions of years later. This absence of structure in an irregular gala xy leads to little density waves in these galaxies. This makes irregular galaxies prime areas to study star formation without the effects of density waves. Collectively they are thought to make up about a quarter of all galaxies. A large chunk of the Local Group is made up of irregular galaxies, most being distant and classified as dwarf irregulars. Irregulars are broken down into two more subcategories along with dwarf. Some irregular galaxies were once spiral or elliptical galaxies but were deformed by an uneven external gravitational force, or may be young galaxies between spiral and elliptical status. Irregular galaxies may contain abundant amounts of gas and dust. This is not necessarily true for dwarf irregulars. Irregular galaxies may also be formed in galaxy collisions. Irregular galaxies are commonly small, about one tenth the mass of the Milky Way galaxy, though there are also unusual cases of large irregulars like UGC 6697. Due to their small sizes, they are prone to environmental effects like colliding with large galaxies and intergalactic clouds.

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Deep dive: Irregular Galaxies This makes irregular galaxies prime areas to study star formation without the effects of density waves. Collectively they are thought to make up about a quarter of all galaxies. A large chunk of the Local Group is made up of irregular galaxies, most being distant and classified as dwarf irregulars. Irregulars are broken down into two more subcategories along with dwarf. Some irregular galaxies were once spiral or elliptical galaxies but were deformed by an uneven external gravitational force, or may be young galaxies between spiral and elliptical status. Irregular galaxies may contain abundant amounts of gas and dust. This is not necessarily true for dwarf irregulars. Irregular galaxies may also be formed in galaxy collisions. Irregular galaxies are commonly small, about one tenth the mass of the Milky Way galaxy, though there are also unusual cases of large irregulars like UGC 6697. Due to their small sizes, they are prone to environmental effects like colliding with large galaxies and intergalactic clouds. Source: https://en.wikipedia.org/wiki/Irregular_galaxy (Wikipedia, CC BY-SA)