Efrain: “You could take a spectrum to see if it’s a G2V star like the Sun, then we would know that it has the same luminosity as the Sun. For example, getting the luminosity of a distant star by knowi...Efrain: “You could take a spectrum to see if it’s a G2V star like the Sun, then we would know that it has the same luminosity as the Sun. For example, getting the luminosity of a distant star by knowing its spectral class (main sequence fitting) depends on finding the luminosity of many closer stars of the same class by means of some other technique (e.g., parallax or moving-cluster method).
