Figure 10-9 Stellar Size and Spectra These spectra are from two stars of the same spectral type (B8) and, hence, the same surface temperature (13,400 K) but different radii and luminosities: (a) the B8 supergiant Rigel (luminosity 58,000 L⊙) in Orion and (b) the B8 main-sequence star Algol (luminosity 100 L⊙) in Perseus.