Boötes I

The Boötes Dwarf Galaxy (Boo I dSph) is a galaxy discovered in 2006, which appears faint, with a luminosity of and an absolute magnitude of –5.8. It lies about 197000 ly away in the constellation Boötes. This dwarf spheroidal galaxy appears to be tidally disrupted by the Milky Way Galaxy, which it orbits, and has two stellar tails that cross over to form a cross. Tidally disrupted galaxies usually only form one tail. The galaxy appears to be significantly elongated, with an ellipticity of.

Like many of the ultrafaint dwarf spheroidals, the entire galaxy appears fainter than the Rigel system (absolute magnitude –7.84). Even so, it is one of the more luminous UFDs. It is metal-poor, like other UFDs, with a mean metallicity of −2.34.

The stellar population of Boötes I is mostly very old stars. The two populations have essentially the same age, 13.4 billion and 13.3 billion years, respectively, with most of the stars being of the latter population.