Boötes I
Galaxy in the constellation Boötes
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The Boötes Dwarf Galaxy (Boo I dSph) is a galaxy discovered in 2006, which appears faint, with a luminosity of 100,000 L☉ and an absolute magnitude of –5.8. It lies about 197,000 light-years (60.4 kiloparsecs) away in the constellation Boötes. This dwarf spheroidal galaxy appears to be tidally disrupted[1] by the Milky Way Galaxy, which it orbits, and has two stellar tails that cross over to form a cross.[citation needed] Tidally disrupted galaxies usually only form one tail.[citation needed] The galaxy appears to be significantly elongated, with an ellipticity of ε = 0.68 ± 0.15.[3]
| Boötes Dwarf Galaxy | |
|---|---|
SDSS image of Boo I | |
| Observation data (J2000 epoch) | |
| Constellation | Boötes |
| Right ascension | 14h 00m 06s[1] |
| Declination | +14° 30′ 00″ ± 15″[1] |
| Distance | 197 ± 18 kly (60 ± 6 kpc)[1] |
| Apparent magnitude (V) | 13.1[a] |
| Characteristics | |
| Type | dSph[1] |
| Apparent size (V) | 26.0′ ± 1.4′[1] |
| Other designations | |
| Boo dSph, Boötes Satellite, Boötes Dwarf Spheroidal Galaxy, Boötes dSph galaxy,[2] PGC 4713553 | |
Like many of the ultrafaint dwarf spheroidals, the entire galaxy appears fainter than the Rigel system (absolute magnitude –7.84).[4] Even so, it is one of the more luminous UFDs.[5] It is metal-poor, like other UFDs, with a mean metallicity of −2.34.[5]
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.[6]
Notes
- ^ Apparent magnitude = Absolute magnitude + Distance modulus = –5.8[1] + 18.9[1] = 13.1