Subject
- extinction2
- galactic center2
- optical astronomy2
- planetary nebulae2
- pre-main sequence stars2
- protostars2
- radio galaxies2
- radio spectroscopy2
- redshifted2
- seyfert galaxies2
- supergiant stars2
- trigonometric parallax2
- atomic physics1
- bl lacertae objects1
- black holes1
- catalogs1
- co line emission1
- exoplanets1
- galaxy classification systems1
- galaxy rotation1
