| Arp 240 | |
| Epoch: | J2000 |
| Ra: | Right: Left: |
| Dec: | Right: Left: |
| Constellation Name: | Virgo |
| Z: | Right: 6798 ± 9 km/s Left: 6757 ± 1 km/s |
| Dist Ly: | Right: 345.1 Mly (105.8 Mpc) Left: 342.1 Mly (104.9 Mpc) |
| Type: | Right: SAB(s)b pec Left: SA(s)b pec |
| Appmag V: | 12.9 / 12.9 |
| Size V: | Right: 1.8′ × 0.9′Left: 1.7′ × 1.1′ |
| Notes: | Interacting galaxies |
| Names: | Right: NGC 5257, UGC 8641, PGC 48330, VV 55b Left: NGC 5258, UGC 8645, PGC 48338, VV 55a |
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. 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.
One supernova has been observed in NGC 5258: SN 2020dko (type Ia, mag. 19).[1]