Spectral Catalog

By observing the spectrum of each star (see Spectroscopy labs), we can determine its spectral type and luminosity class. As we have seen in the previous section, once we know the luminosity of a star, we can calculate its distance. This method (“spectroscopic parallax”) is pretty rough (it has an uncertainty of 25%!), but it is the only available method to measure the distance to stars when their parallax is too small to be detected. Below is a spectral catalog you can use to identify the spectral class of Vega and Capella.

Stellar Spectra Catalog

Below is an HR diagram. Using the spectral classes you found above and the HR diagram below, determine the luminosity of Vega and Capella.