Arp 240

Arp 240 is a pair of interacting spiral galaxies located in the constellation Virgo. The two galaxies are listed together as Arp 240 in the Atlas of Peculiar Galaxies.^[4] The galaxy on the right is known as NGC 5257, while the galaxy on the left is known as NGC 5258. Both galaxies are distorted by the gravitational interaction, and both are connected by a tidal bridge, as can be seen in images of these galaxies.

Arp 240
Arp 240. The two galaxies are NGC 5257 (right) and NGC 5258 (left).
Observation data (J2000 epoch)
Constellation	Virgo
Right ascension	Right: 13h 39m 52.3s[1] Left: 13h 39m 57.7s[2]
Declination	Right: +00° 50′ 22″[1] Left: +00° 49′ 51″[2]
Redshift	Right: 6798 ± 9 km/s[1] Left: 6757 ± 1 km/s[2]
Distance	Right: 345.1 Mly (105.8 Mpc)[3] Left: 342.1 Mly (104.9 Mpc)[3]
Apparent magnitude (V)	12.9 / 12.9[1][2]
Characteristics
Type	Right: SAB(s)b pec[1] Left: SA(s)b pec[2]
Apparent size (V)	Right: 1.8′ × 0.9′[1]Left: 1.7′ × 1.1′[1]
Notable features	Interacting galaxies
Other designations
Right: NGC 5257, UGC 8641, PGC 48330, VV 55b[1] Left: NGC 5258, UGC 8645, PGC 48338, VV 55a[1]

One supernova has been observed in NGC 5258: SN 2020dko (type Ia, mag. 19).^[5]