NGC 4651

NGC 4651 is a spiral galaxy located in the constellation of Coma Berenices that can be seen with amateur telescopes, at a distance not well determined that ranges from 35 million light years^[2] to 72 million light years.^[3] It was discovered by German-British astronomer William Herschel on 30 December 1783.^[4]

NGC 4651
NGC 4651. Note the umbrella-shaped stream.
Observation data (J2000 epoch)
Constellation	Coma Berenices
Right ascension	12h 43m 42.6766s[1]
Declination	+16° 23′ 36.222″[1]
Redshift	0.002669[1]
Heliocentric radial velocity	800 ± 1 km/s[1]
Distance	74.20 ± 3.50 Mly (22.749 ± 1.074 Mpc)[1]
Apparent magnitude (V)	11.39[1]
Characteristics
Type	SA(rs)c[1]
Size	~87,900 ly (26.95 kpc) (estimated)[1]
Apparent size (V)	4.0′ × 2.6′[1]
Other designations
Umbrella Galaxy, IRAS 12412+1639, Arp 189, UGC 7901, MCG +03-33-001, PGC 42833, CGCG 100-004, VV 56[1]

NGC 4651 imaged by the Hubble Space Telescope

Spiral galaxy NGC 4651. Credit: ESA / Hubble Space Telescope & NASA, D. Leonard

Features

This member of the Virgo Cluster, located on its outskirts,^[5] is known as the Umbrella Galaxy due to the umbrella-shaped structure that extends from its disk to the east and that is composed of stellar streams, being the remnants of a much smaller galaxy that has been torn apart by NGC 4651's tidal forces,^[2][6] something that explains why NGC 4651 has been included on Halton Arp's Atlas of Peculiar Galaxies as Arp 189 -galaxy with filaments-.

Studies using radiotelescopes of the distribution of its neutral hydrogen show distortions on NGC 4651's outer regions and a gas clump associated with a dwarf galaxy that may have been born in the event that produced the mentioned stellar streams.^[7]

Unlike most spiral galaxies of the Virgo Cluster, NGC 4651 is rich in neutral hydrogen, also extending beyond the optical disk,^[7] and its star formation is typical for a galaxy of its type.^[5]

Supernovae

Two supernovae have been observed in NGC 4651:

• SN 1987K (Type II, mag. 15) was discovered by Carlton Pennypacker on 28 July 1987.^[8][9]
• SN 2006my (Type II, mag. 15.3) was discovered by Kōichi Itagaki on 8 November 2006.^[10][11]