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Sunday, July 25, 2021

What is a Dwarf galaxy?


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Dwarf galaxies

Dwarf galaxies are smaller celestial bodies, consisting of roughly a thousand to several billion stars, in contrast to the 200-400 billion stars found in more sizable galaxies like the Milky Way. One such dwarf galaxy, the Large Magellanic Cloud, orbits the Milky Way and is home to more than 30 billion stars. Despite its size, it is sometimes considered a fully-fledged galaxy, not a dwarf galaxy, due to its significant star count. The formation and activities of dwarf galaxies are believed to be largely driven by their interaction with these larger galaxies. There are various classifications of dwarf galaxies based on their shape and composition.



Formation of Dwarf Galaxies

Dwarf galaxies such as NGC 5264 typically contain around one billion stars. The popular theory suggests that these galaxies, including dwarf galaxies, are created in conjunction with dark matter or from metallic gas. In a surprising discovery, NASA's Galaxy Evolution Explorer space probe found new dwarf galaxies being formed from gases with low metal content. These galaxies were found in the Leo Ring, a hydrogen and helium cloud surrounding two large galaxies in the Leo constellation.


Due to their diminutive size, dwarf galaxies often experience gravitational pull and disruption from neighboring spiral galaxies, leading to galaxy mergers.


Local Dwarf Galaxies and Their Characteristics

The Phoenix Dwarf Galaxy, a type of dwarf irregular galaxy, has a unique characteristic: younger stars are concentrated in its inner regions, while older stars occupy the outskirts.


The Local Group contains numerous dwarf galaxies that commonly orbit larger galaxies, such as the Milky Way, Andromeda Galaxy, and the Triangulum Galaxy. A study conducted in 2007 suggested that many dwarf galaxies resulted from galactic tides during the initial evolution stages of the Milky Way and Andromeda. Tidal dwarf galaxies occur when galaxies collide, and their gravitational masses interact, pulling galactic material away from the parent galaxies and their surrounding dark matter halos. Interestingly, a 2018 study proposes that some local dwarf galaxies were formed incredibly early, during the Dark Ages within the first billion years post-big bang.


Over 20 known dwarf galaxies orbit the Milky Way. Recent observations have led astronomers to theorize that the Milky Way's largest globular cluster, Omega Centauri, might be the core of a dwarf galaxy with a central black hole, which was eventually absorbed by the Milky Way.



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