A group of galaxies nicknamed the Copeland Septet, in the constellation of Leo.[1]
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| Observation data (Epoch J2000) | |
|---|---|
| Constellation(s) | Leo |
| Right ascension | 11h37m 50.5s[2] |
| Declination | +21° 59′ 06″[2] |
| Brightest member | NGC 3753[3] |
| Redshift | 0.0304[4] |
| Distance | 132 Mpc (431 Mly) h−1 67.3[3] |
| Binding mass | (6.1±1.0)×1014 h−1 50.00[4] M☉ |
| X-ray luminosity | 1041.98 erg·s−1[4] |
| Other designations | |
| HCG 57 | |
| See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters | |
The Copeland Septet (also Copeland's Septet, Hickson Compact Group 57) is a group of galaxies in the constellation Leo that includes NGC 3748, NGC 3754, NGC 3750, NGC 3751, NGC 3745, NGC 3753 and NGC 3746.[5][6] The group was discovered by British astronomer Ralph Copeland in 1874. The location of Copeland's Septet is right ascension 11h37m50s / declination +21° 59′ (2000.0), about three degrees northwest of third magnitude star 93 Leonis.
The redshift of the brightest member, NGC 3753 places Copelands Septet as a part of the Coma Supercluster.[7]
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