| Emission nebula | |
|---|---|
| Planetary nebula | |
 Abell 31 as seen from the Mount Lemmon Observatory | |
| Observation data: J2000 epoch | |
| Right ascension | 08h 54m 11.4s |
| Declination | +08° 54′ 30″ |
| Apparent magnitude (V) | 15.5 [1] |
| Apparent dimensions (V) | 16.2′ [1] |
| Constellation | Cancer |
| Physical characteristics | |
| Radius | 10 ly |
| Notable features | A very large and colorful PN |
| Designations | Sh2-290, PK 219.1+31.2, A 31, ARO 135 |
Abell 31 (also known as Sh2-290 or PK 219+31.1 [2] ) is an ancient planetary nebula in the constellation of Cancer. It is estimated to be about 2,000 light years away. The central white dwarf has a spectral type of DAO. [3]
Abell 31 is mainly composed of hydrogen and oxygen gas. [4] The blue oxygen occupies the central region and makes up the bulk of the nebula, while the red hydrogen makes a ring at the nebula's edge. This object is very old, and consequently, it is very large and dim (specifically, it has a low surface brightness), and its gas is dispersing into the interstellar medium. [5]
Some astronomical objects that appear nearby from our perspective include star clusters Messier 44 and 67, and galaxies NGC 2731 and IC 523, among many others. [6]
