Extra-galactic Variable Stars

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

StarTypeRangeNotes
AE And SDOR15.1 – 17.6In M31
AF And SDOR15.4 – 17.6In M31
M31N 2008-12a NR18.0 – <23In M31

Active galactic nuclei

AGNTypeRangeNotes
Mrk 421 BLLAC12.0 – 13.9Markarian 421