Ursa Major II Dwarf

Ursa Major II Dwarf (UMa II dSph) is a dwarf spheroidal galaxy situated in the Ursa Major constellation and discovered in 2006 in the data obtained by the Sloan Digital Sky Survey.

[3] Ursa Major II is one of the smallest and faintest satellites[note 1] of the Milky Way—its integrated luminosity is about 4000 times that of the Sun (absolute visible magnitude of about −4.2),[2] which is much lower than the luminosity of the majority of globular clusters.

[2] The stellar population of UMa II consists mainly of old stars formed at least 10 billion years ago.

[2] The metallicity of these old stars is also very low at [Fe/H] ≈ −2.44 ± 0.06, which means that they contain 300 times less heavy elements than the Sun.

The measurements have so far failed to detect any neutral hydrogen in it—the upper limit is only 562 solar masses.