Arp 268 (Gary Imm)

Celestial hemisphere: Northern · Constellation: Ursa Major (UMa)

Arp 268

This object is a dwarf irregular galaxy located "only" 10 million light-years away in the constellation of Ursa Major. Its apparent diameter is 8 minutes and its actual diameter is 25,000 light years. It has an apparent magnitude of 12 and a low surface brightness of 24.

This object has several identifiers, including Arp 268 and UGC 4305, but its most common name is Holmberg II. Erik Holmberg (1908 – 2000) was a Swedish astronomer who is most famous for his work on the effects of interacting galaxies. The nine low surface brightness galaxies existing in the Holmberg catalog were detected by Holmberg at the Lund Observatory in Sweden. The galaxies were published in three publications from 1950 to 1969.

Because it is so close, we have a peak inside at an unusual amount of galaxy detail, including bubbly pink Ha regions and blue star clusters. Star formation is active in this galaxy. The most interesting thing to me about this image are the giant bubbles of glowing Ha gas, particularly the curving line of bubbles at the top of the galaxy in this image. These bubbles reach sizes up to several thousand light years in diameter. They surround high mass stars which are expelling strong stellar winds. Unlike a spiral or elliptical galaxy, this dwarf galaxy has a weak gravitational field which allows these bubbles to retain their shape.

Several other small galaxies are also visible in the background.

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Status	Advanced success
Started	...
Astrometry.net job	2537482
PixInsight job	WMC84FGW3PMMSYU3D0XUMHZFQRQLC7IT
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	08h19m03s.701
RA (top/left)	08h19m41s.331
RA (top/right)	08h22m44s.254
RA (bottom/right)	08h18m24s.878
RA (bottom/left)	08h15m25s.464

Dec (center)	+70°43′15″.62
Dec (top/left)	+70°24′16″.83
Dec (top/right)	+70°49′35″.75
Dec (bottom/right)	+71°02′13″.68
Dec (bottom/left)	+70°36′39″.29

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Arp 268

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