Ursa Major II Dwarf
Ursa Major II ( UMa II also short ) is a spheroidal dwarf galaxy ( dSph ) in the constellation of the Great Bear and was discovered in 2006 after analysis of the imaging survey of the Sloan Digital Sky Survey.
Properties
The galaxy is approximately 30 kpc away from our solar system and moves on this at a speed of about 116 km / s. She has because of their spheroidal property pc in about an elliptical axis ratio of 2:1 with a half-light radius of only about 140. UMa II, making it one of the smallest and faintest satellites of the Milky Way (only Com, Segue 1, Segue 2, boat II and Willman 1 are lichtschwächser ). The integral brightness of the dwarf galaxy is approximately equal to the 4000 -fold of the sun, which corresponds to an absolute magnitude of -4.2 m. This is significantly less than the luminosity of most globular clusters. UMa II is even fainter than some individual stars such as Canopus in the constellation keel of the ship. Comparable she is in the luminosity with Bellatrix in the constellation Orion.
On the other hand, the galaxy has a mass of 5 million solar masses what a mass-luminosity ratio of about 2000 is tantamount, which would make the galaxy to an extremely strong dominated by dark matter object. This could also turn out as a misjudgment, however, if the dwarf galaxy may no longer located in virial equilibrium. The fact that she is already disturbed by the tidal forces acting on it, is apparent in their batch irregularity.
The stellar population of UMA II consists mainly of old stars together, which arose prior to at least 10 billion years ago. The metallicity of this population proves to be extremely metal-poor with [Fe / H] ≈ -2.44 ± 0.06. The sun has about 300 times more heavy elements. So are the stars of this galaxy to the first stars ever, which originated in the cosmos. Currently arise in the Ursa Majoris II dwarf galaxy no more stars, could also not a neutral hydrogen gas in the galaxy are found. The upper limit of detection would amount currently lobbying to only 562 solar masses.
More
- List of satellite galaxies of the Milky Way
- List of galaxies of the Local Group