NGC 6822, or Barnard's Galaxy, is an irregular dwarf galaxy and one of the closest galaxies to the Milky Way. This collection of approximately 10 million stars shines at magnitude 9 in the constellation Sagittarius.
Basic Facts About Barnard's Galaxy
NGC 6822 is an irregular dwarf galaxy because of its small size and undefined shape. Its 10 million stars is a far cry from a galaxy such as the Milky Way with up to 400 billion stars or the even larger Andromeda Galaxy, which is home to about 1 trillion stars. Barnard's Galaxy is only about a tenth the size of the Milky Way but dwarf galaxies in general are much more numerous in the Universe than huge spirals such as our home galaxy and Andromeda.
NGC 6822 is found in the corner of the constellation Sagittarius. It lies 1.6 million light-years away. The Andromeda Galaxy is nearly twice that distance from the Milky Way. Both galaxies, however, are members of the Local Group.
The galaxy is named for American astronomer Edward Emerson Barnard, who spotted it in his 125-millimeter telescope in 1884.
Red Nebulae in NGC 6822
The most notable features in Barnard's Galaxy are the red bubbles. The red bubbles are areas where stars are being formed. As the solar winds of these stars switch on, they heat the gas and clear their immediate surroundings of gas and dust, creating the bubbly nebulae. The most prominent red bubble nebulae, seen in this image in the upper left hand corner, has a cluster of massive, scorching stars at its center, which are sending waves of matter that crash into the surrounding interstellar material, creating the glowing ring-like structure.
Irregular Dwarf Galaxies
Irregular dwarf galaxies such as NGC 6822 get their discombobulated shapes from interactions with other galaxies. Barnard's Galaxy may have initially been part of another galaxy entirely that had stars stripped off it and flung away after a close pass with a different galaxy. Because a number of dwarf galaxies are close to the Milky Way, they are a good source for astronomers to study. They are currently about 14 known dwarf galaxies orbiting the Milky Way.
Omega Centauri, once believed to be a globular cluster, may turn out to be a dwarf galaxy circling the Milky Way too. Observations in 2008 showed that it appears to have a black hole at its center, and may therefore be similar to Barnard's Galaxy and other dwarf galaxies in the Local Group that have had their bulk shaved off, stripped away, or otherwise mangled through interactions with the Milky Way.
Source: ESO
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