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 |
M31N 2008-12a | NR | 18.0 – <23 | In M31 |
Active galactic nuclei
AGN | Type | Range | Notes |
---|---|---|---|
Mrk 421 | BLLAC | 12.0 – 13.9 | Markarian 421 |