NGC 4490

NGC 4490, also known as the Cocoon Galaxy, is a barred spiral galaxy in the constellation Canes Venatici. It was discovered by German-British astronomer William Herschel on 14 January 1788.^[2] It is known to be of the closest interacting/merging galactic system. The galaxy lies at a distance of 25 million light years from Earth making it located in the local universe. It interacts with its smaller companion NGC 4485 and as a result is a starburst galaxy. NGC 4490 and NGC 4485 are collectively known in the Atlas of Peculiar Galaxies as Arp 269. The two galaxies have already made their closest approach and are rushing away from each other. It has been discovered that NGC 4490 has a double nucleus.^[3]

NGC 4490
NGC 4490 and satellite galaxy, NGC 4485
Observation data (J2000 epoch)
Constellation	Canes Venatici
Right ascension	12h 30m 36.2390s[1]
Declination	41° 38′ 38.032″[1]
Redshift	0.001885[1]
Heliocentric radial velocity	565 ± 3 km/s[1]
Distance	25.1 ± 5.0 Mly (7.7 ± 1.5 Mpc)[1]
Apparent magnitude (V)	9.8
Characteristics
Type	SB(s)d pec [1]
Size	~40,200 ly (12.34 kpc) (estimated)[1]
Apparent size (V)	6.3′ × 3.1′[1]
Other designations
HOLM 414A, IRAS 12281+4155, Arp 269 NED02, UGC 7651, MCG +07-26-014, PGC 41333, CGCG 216-008, VV 030a[1]

NGC 4490 is located 3/4° northwest of beta Canum Venaticorum and with apparent visual magnitude 9.8, can be observed with 15x100 binoculars.^[4] It is a member of the Herschel 400 Catalogue. It belongs to the Canes II Group. NGC 4490 has a system of satellite galaxies oriented roughly in a plane.^[5]

Stellar stream

A stellar stream 25,000 light years long connects the two interacting galaxies. The stellar stream is made of bright knots and large gas rich pockets. Young blue hot massive stars are formed in this region.^[6]

Supernovae and Luminous Red Nova

Two supernovae and one luminous red nova (LRN) have been observed in NGC 4490:

• SN 1982F (type unknown, mag. 16) was discovered by Paul Wild on 15 April 1982.^[7][8]
• AT 2011kp (type LRN, mag. 16.7) was discovered by Giancarlo Cortini and Stefano Antonellini on 16 August 2011.^[9][10]
• SN 2008ax (Type II, mag. 13) was discovered by the Lick Observatory Supernova Search (LOSS) on 3 March 2008^[11] and by Kōichi Itagaki on 4 March 2008.^[12][13][14]

Gallery

• 
  Extreme tidal forces have carved out the shapes and properties of NGC 4490.^[15]

See also

• Barred spiral galaxy
• Canes Venatici (constellation)