Anne’s Picture of the Day: Dwarf Galaxy UGC 5497

(Before It's News)

read more at Anne’s Astronomy News http://annesastronomynews.com/

May 13, 2013

UGC 5497, a dwarf galaxy in Ursa Major

Image Credit: ESA/Hubble & NASA

UGC 5497 is a compact blue dwarf galaxy, located about 12 million light-years away from Earth in the constellation of Ursa Major (the Great Bear). It is a member of the M81 Group of galaxies, one of the nearest groups to the Local Group of which our Milky Way is a member.

This rather faint dwarf galaxy contains lots of newly formed clusters of stars, probably no more than a few million years old. The bright, blue stars that arise in these clusters help to give the galaxy an overall bluish appearance. But, because most of the stars in UGC 5497 are massive, they only remain stable for a few million years, before they start exploding as supernovae, which means that this blue dwarf will not retain its appearance for long.

When these massive stars explode, they will start dispersing the gas currently fueling the formation of new stars, and the galaxy will stop growing.

According to the leading cosmological theory of galaxy formation there should be tens or hundreds of dwarf galaxies orbiting big galaxies like Messier 81 (and the Milky Way). However, observations conducted thus far failed to reveal such large numbers of satellites.

So, back in 2008, a team of astronomers were looking for new dwarf galaxy candidates associated with Messier 81 (Bode’s Galaxy) in a ground-based telescope survey. They detected 22 new dwarf galaxy candidates, including UGC 5497.

Previously overlooked objects such as this one may be part of the large number of dwarf galaxies estimated to exist around larger galaxies. However, astronomers remain puzzled over the so-called “missing satellite” problem.

This composite image was taken in late 2009 with the Advanced Camera for Surveys on the Hubble Space Telescope, using infrared and optical filters.

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