Segue 3
Star cluster
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Segue 3 is a faint star cluster of the Milky Way galaxy discovered in 2010 in data obtained by Sloan Digital Sky Survey.[1] It is located in the Pegasus constellation about 17 kpc from the Sun and is moving away from it at 167.1 ± 1.5 km/s.[2]
| Segue 3 | |
|---|---|
| Observation data (J2000 epoch) | |
| Constellation | Pegasus |
| Right ascension | 21h 21m 31s[1] |
| Declination | 19° 07′ 02″[1] |
| Distance | 55.1 ± 2.3 kly (16.9 ± 0.7 kpc[2]) |
| Apparent magnitude (V) | 14.9[1] |
| Apparent dimensions (V) | 52 ± 10″ (half-light diameter)[2] |
| Physical characteristics | |
| Radius | 6.8 ± 1.3 ly (2.1 ± 0.4 pc)[2] |
| Other designations | Segue 3 |
Segue 3 is extremely faint—its visible absolute magnitude is estimated at −1.2[1] or even at about 0.0 ± 0.8,[2] which means that the cluster is only 100 to 250 times brighter than the Sun. Its small radius—of about 2.1 pc—is typical for galactic globular clusters.[2] The cluster has a slightly flattened shape and shows some evidence of tidal disruption.[2]
The metallicity of Segue's 3 stars is [Fe/H] ≈ −1.7, which means that they contain 70 times less heavy elements than the Sun. These stars are more than 12 billion year old.[2] Segue 3 appears to be one of the faintest globular clusters of the Milky Way.