Zwicky's Triplet

Zwicky's Triplet (Arp 103^[2]) is a group of three galaxies visible in the constellation Hercules.^[3][4] None of the galaxies is listed in the New General Catalogue (NGC) or Index Catalogue (IC), but all three are identified in the Catalogue of Principal Galaxies (PGC) published in 1989.

Zwicky's Triplet
Observation data (Epoch )
Constellation(s)	Hercules
Right ascension	16h 49m 28.3s[1]
Declination	+45° 27′ 40″[1]
Brightest member	PGC 59061

Arp 103’s brightest member is PGC 59061, at magnitude 15. Overlapping it on its southwestern flank is PGC 59062, which is smaller and fainter. Two arcminutes to the north of this pair is PGC 59065, a lenticular galaxy of magnitude 16. A faintly luminous tidal arm of intergalactic matter stretches between PGC 59061 and PGC 59065.^[5]

The other Zwicky's Triplet

IC 3481 at 12h 32m, +11° 24' (2000.0) in Virgo, which is connected to PGC 41646 ("IC 3481A") as the system Arp 175, but probably not connected to IC 3483, is sometimes called Zwicky's Triplet, but this name is more often applied to the system at 16h 49m, +45° 30' (2000.0) in Hercules.^[6][7]

See also

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