A large number of variable stars in galaxies other than the Milky Way can usefully be observed by amateur astronomers. These are the objects on my observing program.
Historically, some star-like objects of varying brightness were catalogued as variable stars. BL Lac is a famous example; others include AP Lib and W Com. They were subsequently found not to be stars at all but the nuclei of galaxies. The optically varying component of the light from the nucleus comes from a relativistic jet of particles being expelled from the vicinity of a supermassive black hole. BL Lac is now catalogued as a blazar, as is Markarian 421 which appears below. Quasars form another species in the AGN (active galactic nuclei) zoo, of which 3C 271 is the brightest and best known.
Stars
| Star | Type | Range | Notes |
|---|---|---|---|
| AE And | SDOR | 15.1 – 17.6 | In M31 |
| AF And | SDOR | 15.4 – 17.6 | In M31 |
| V0619 And | SRB | 15.4 – 17.6 | In M31 |
| M31N 2008-12a | NR | 18.0 – <23 | In M31 |
| Y Tri | SDOR | 15.4 – 19.1 | In M33 |
Supernovae
| Supernova | Type | Range | Notes |
|---|---|---|---|
| SN2022qmx | SN Ia | ≤ 18.6 | Strongly gravitationally lensed SN at z=0.35 and likely enhanced by 3 magnitudes. |
| SN2023ixf | SN II-L | 12.0 – <22 | In M101 |
Active galactic nuclei
| AGN | Type | Range | Notes |
|---|---|---|---|
| Mrk 421 | BLLAC | 12.0 – 13.9 | |
| BL Lac | BLLAC | 11.9 – 16.3 | |
| 4C 31.03 | AGN | 12.4 – 19.0 |