Straight From the Island of Misfit Galaxies: Barnard

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By galactic standards, Barnard is a misfit. This galaxy is diminutive, oddly shaped, and hard to see. But give the little box-shaped guy credit: this dwarf galaxy has no shortage of stellar splendor and pyrotechnics. Some feisty star formation is taking place, and a few curious nebulae dot the landscape with scorching stars sending waves of matter smashing into the surrounding stellar material. Plus, Barnard has a storied past: it likely was the victim of cannibalization. But cosmic misfits like Barnard’s Galaxy help researchers understand how galaxies interact, evolve and occasionally feed on each other, leaving behind radiant, star-filled scraps.

In this new image from ESO, Barnard’s Galaxy glows beneath a sea of foreground stars in the direction of the constellation of Sagittarius (the Archer). Also known as NGC 6822, the nicknamed comes its discoverer, American astronomer Edward Emerson Barnard, who spied it with his 125-millimeter aperture refractor in 1884. At the relatively close distance of about 1.6 million light-years, Barnard’s Galaxy is a member of the Local Group (ESO 11/96), the archipelago of galaxies that includes our home, the Milky Way.

Astronomers obtained this latest portrait using the Wide Field Imager (WFI) attached to the 2.2-metre MPG/ESO telescope at ESO’s La Silla Observatory in northern Chile.

At only about a tenth of the Milky Way’s size, Barnard’s Galaxy fits its dwarfish classification. All told, it contains about 10 million stars — a far cry from the Milky Way’s estimated 400 billion. In the Local Group, as elsewhere in the Universe, however, dwarf galaxies outnumber their larger, shapelier cousins, such as the Milky Way, the Andromeda and the Triangulum galaxies.

Even though Barnard’s Galaxy lacks the majestic spiral arms and glowing, central bulge that grace its big galactic neighbors, the Milky Way, the Andromeda and the Triangulum galaxies, there is a lot going on in this dwarf galaxy.

Reddish nebulae in this image reveal regions of active star formation, where young, hot stars heat up nearby gas clouds. Also prominent in the upper left of this new image is a striking bubble-shaped nebula. At the nebula’s centre, a clutch of massive, scorching stars send waves of matter smashing into the surrounding interstellar material, generating a glowing structure that appears ring-like from our perspective. Other similar ripples of heated matter thrown out by feisty young stars are dotted across Barnard’s Galaxy.

Irregular dwarf galaxies like Barnard’s Galaxy get their random, blob-like forms from close encounters with or “digestion” by other galaxies. Like everything else in the Universe, galaxies are in motion, and they often make close passes or even go through one another. The density of stars in galaxies is quite low, meaning that few stars physically collide during these cosmic dust-ups. Gravity’s fatal attraction, however, can dramatically warp and scramble the shapes of the passing or crashing galaxies. Groups of stars are pulled or flung from their galactic home, in turn forming irregularly shaped dwarf galaxies like NGC 6822.

Click here to see a zoom-in video (choose from various formats) of Barnard’s Galaxy.

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. North is up, East to the left.

Source: ESO