Ultra-compact dwarf galaxy discovered
1 Nov 2013 by Evoluted New Media
An ultra-compact dwarf galaxy with a density of stars 15,000 times greater than the Milky Way has been discovered by astronomers from Michigan State University.
The galaxy – dubbed M60-UCD1 – was found in the Virgo cluster, located about 54 million light years from the Milky Way. Astronomers say it is remarkable because about half of its mass is located within a radius of 80 light years.
“This galaxy is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe,” said Jay Strader, assistant professor of physics and astronomy.
Astronomers are trying to determine if M60-UCD1 and other ultra-compact dwarf galaxies are naturally born as jam-packed star clusters, or if they are galaxies that shrink because stars are ripped away from them. A possible massive black hole – combined with the high galaxy mass and sun-like levels of elements found in the stars – favour the latter.
M60-UCD1 has a bright X-ray source at its centre – possibly a giant black hole weighing in at some 10 million times the mass of our sun. If correct, it helps tip the scales against a star cluster since such large black holes aren’t found in these types of objects.
“The significant of the X-ray source is that it shows the possible presence of a massive central black hole, much like the one at the centre of our own Milky Way galaxy,” Strader told Laboratory News. “Few central black holes have been confirmed in dwarf galaxies. Further work on M60-UCD1 to confirm this candidate black hole would suggest that massive central black holes are common in dwarf galaxies – essentially opening up a new class of galaxies to study black holes in. This in turn will better constrain theories of the formation of black holes in all galaxies.”
The galaxy was discovered using the Hubble Space Telescope, with follow-up observations using Chandra X-ray Observatory and ground-based optical telescopes.
“Twenty years ago we couldn’t have done this,” Strader said. “We didn’t have Hubble or Chandra. This is one of those projects where you bring together the full force of NASA’s great observatories, plus ground-based resources.”
The finding was published in Astrophysical Journal Letters. http://iopscience.iop.org/2041-8205/
