Image Credit & Copyright: NASA/ESA Hubble Space Telescope.
Any idea what this is? Nope, it’s not a huge globular star cluster; it’s actually an entire galaxy. Ok, calling it a galaxy may need a little clarification. It’s what’s known as a Compact Blue Dwarf Galaxy and it was just discovered back in 2008 while searching for companion galaxies to M81 (Bodes Galaxy). It’s pretty amazing that something of this size can go unnoticed for so long but take into consideration its small stature and diffuse appearance, at 12 million light years I can see how it stayed out of the limelight when it wasn’t actively being sought out.
The Lambda Cold Dark Matter theory, which is the current leading theory of galaxy formation, says that there should be many more satellite dwarf galaxies (upwards of 100) around large galaxies like Andromeda, M81 and the Milky Way. This problem has taken on the name of the “Missing Satellite Problem” and even though a few handfuls of new dwarf galaxies have been discovered, it’s nowhere near the amount calculated to be there.
If you enlarge this image and have a look around you will see many distant galaxies faintly dotting the background as well as the seemingly bright foreground Milky Way star to the right.
NAME: UGC 5497.
WHAT IS IT?: Compact Blue Dwarf Galaxy.
HOW BIG IS IT?: Few million stars.
HOW FAR AWAY IS IT?: About 12 million light years.
WHERE IS IT? (General): Constellation Ursa Major (The Great Bear). Is part of the M81 Group of Galaxies.
WHERE IS IT? (Exact RA/DEC J2000): RA 10h 12m 48.48s / DEC +64° 06′ 26.8”.
ESA Space Telescope page for this image: http://www.spacetelescope.org/images/potw1224a/
NASA page for this image: http://www.nasa.gov/mission_pages/hubble/science/ugc5497.html