Subject
- planetary nebulae37
- stellar spectral types36
- exoplanets35
- trigonometric parallax35
- m stars34
- atomic physics33
- extinction30
- horizontal branch stars30
- carbon stars29
- ultraviolet astronomy29
- apparent magnitude26
- supernovae26
- f stars25
- quasars25
- interstellar reddening24
- stellar associations24
- galaxy clusters23
- infrared sources22
- catalogs21
- galaxy classification systems19
