NGC 474

NGC 474 is an elliptical galaxy about 100 million light years distant in the constellation Pisces. This large galaxy is known to possess tidal shells^[5] and tidal tails, although their origins remain unclear.^[2] One possible explanation is that NGC 474 interacted with a galaxy several billion years ago.^[6]

NGC 474
A Hubble Space Telescope image of NGC 474
Observation data (J2000[1] epoch)
Constellation	Pisces[2]
Right ascension	01h 20m 06.7s[1]
Declination	+03° 24′ 58″[1]
Redshift	0.007755[1]
Heliocentric radial velocity	2325 km/s ±7 km/s[1]
Galactocentric velocity	2398 km/s ±7 km/s[1]
Distance	~100 Mly (~31 Mpc)[2]
Characteristics
Type	S0[3]
Size	250,000 ly (diameter)[4]
Other designations
Arp 227, MCG 0-4-85, PGC 4801, UGC 864, ZWG 385.71[3]

Structure

The origins of the spectacular tidal features around NGC 474 have been extensively studied, and some possible explanations have been published. The authors of one study argued that the tidal tails were formed because of a collision with a galaxy 2 billion years ago.^[6] The same study also stated that NGC 474 is absorbing gas from its neighbor, NGC 470, since the ancient collision. ^[6] In another model, the tidal shells can be explained by a gas-rich spiral galaxy colliding with NGC 474 twice, before finally merging.^[5] NGC 474 is moving away from the Sun at a rate of 2412 km/s due to dark energy.^[7]

NGC 474's (right) tidal tails and shell-like structures may be from collision(s) with another galaxy. A neighboring spiral galaxy, NGC 470, is on the left.

In July 2017 a Type Ia supernova designated SN 2017fgc was discovered in NGC 474.^[8] It was located at a considerable distance from the galactic nucleus.^[9]

Further reading

• Turnbull, A. J.; Carter, D.; Bridges, T. J.; Thomson, R. C. (1999) Shell Formation in NGC474