Copeland Septet

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 11^h 37^m 50^s / declination +21° 59′ (2000.0), about three degrees northwest of third magnitude star 93 Leonis.

A group of galaxies nicknamed the Copeland Septet, in the constellation of Leo.[1]
Observation data (Epoch J2000)
Constellation(s)	Leo
Right ascension	11h 37m 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

The redshift of the brightest member, NGC 3753 places Copelands Septet as a part of the Coma Supercluster.^[7]

See also

• Wild's Triplet
• Zwicky's Triplet
• Robert's Quartet
• Stephan's Quintet and NGC 7331 Group (also known as the Deer Lick Group located about half a degree northeast of Stephan's Quintet)
• Seyfert's Sextet