| Andromeda I | |
|---|---|
 Part of Andromeda I by theHST | |
| Observation data (J2000epoch) | |
| Constellation | Andromeda |
| Right ascension | 00h 45m 39.8s[1] |
| Declination | +38° 02′ 28″[1] |
| Redshift | -368 ± 11 km/s[1] |
| Distance | 2.40 ± 0.08Mly (735 ± 23kpc)[2][3][4] |
| Apparent magnitude (V) | 13.6[1] |
| Characteristics | |
| Type | dSph |
| Apparent size (V) | 2.5′ × 2.5′[1] |
| Notable features | satellite galaxy ofM31 |
| Other designations | |
| And I,[2] Anon 0043+37,[1]PGC 2666[1] | |
Andromeda I is adwarf spheroidal galaxy (dSph)[5] about 2.40[4] millionlight-years away in theconstellationAndromeda. Andromeda I is part of thelocal group of galaxies and asatellite galaxy of theAndromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31.[6] As of 2005, it is the closest knowndSph companion to M31[7] at an estimated projected distance of ~40[4]kpc or ~150,000[6] light-years.
Andromeda I was discovered bySidney van den Bergh[8] in 1970 with theMount Palomar Observatory 48-inchtelescope.[5] Further study of Andromeda I was done by theWFPC2camera of theHubble Space Telescope. This found that thehorizontal branch stars, like other dwarf spheroidal galaxies were predominantly red.[9] From this, and the abundance of bluehorizontal branch stars, along with 99RR Lyrae stars detected in 2005,[7] lead to the conclusion there was an extended epoch ofstar formation. The estimated age is approximately 10Gyr. The Hubble Space Telescope also found aglobular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.[10]
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| Location | Andromeda Galaxy → Andromeda subgroup →Local Group →Local Sheet →Local Volume →Virgo Supercluster →Laniakea Supercluster →Pisces–Cetus Supercluster Complex →Local Hole →Observable universe →Universe Each → may be read as "within" or "part of". | .jpg) |
|---|---|---|
| Satellite galaxies |
*It is uncertain whether these are companion galaxies of the Andromeda Galaxy | |
| Catalogued stars | ||
| Other | ||
