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The Milky Way's tiny but tough neighbour
DR EMILY BALDWIN
ASTRONOMY NOW
Posted: October 14, 2009


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ESO has today released a stunning new image of the Milky Way's neighbouring Barnard's galaxy, revealing curious bubble-like nebulae and regions of rich star formation.

Barnard’s galaxy glows beneath a sea of foreground stars in the direction of the constellation of Sagittarius (the Archer). The image was made from data obtained through four different filters (B, V, R, and H-alpha). The field of view is 35 x 34 arcmin. Image: ESO.

Also known as NGC 6822, Barnard's galaxy falls into the category of irregular dwarf galaxies due to its odd shape and relatively small size by cosmic standards – it is about a tenth the size of the Milky Way, hosting around 10 million stars compared with the Milky Way's estimated 400 billion. The individual 'personalities' of these galactic oddities reveal the subtleties of how galaxies interact, evolve and occasionally consume one another.

Despite its lack of spiral arms Barnard's galaxy has no shortage of stellar splendour. Pockets of active star formation are given away by red glowing nebulae that are heated up by the hot young stars. Floating at the upper left of this new image is a striking bubble-shaped nebula, blown out by a crop of massive blazing stars at its heart. These powerhouses are sending waves of matter smashing into the surrounding interstellar material, generating a glowing structure that appears ring-like from our perspective. Other less prominent bubbles of heated material can be seen dotted across the galaxy.

Irregular shaped galaxies like NGC 6822 gain their random form as a result of close encounters with passing galaxies that see the gravitational might of the predatory galaxy seizing stars from another, pulling them from their home and flinging them away to perhaps form a new irregularly shaped dwarf galaxy. In some cases one galaxy may consume another, scrambling up the shapes of both galaxies and resulting in a deformed, single galaxy.

Barnard’s galaxy is a member of the Local Group, the archipelago of galaxies that includes our home, the Milky Way, and resides at a distance of about 1.6 million light-years. Astronomers obtained this latest portrait using the Wide Field Imager (WFI) attached to the 2.2-meter MPG/ESO telescope at ESO’s La Silla Observatory in northern Chile.