Using Spitzer, the astronomers were able to estimate the stellar masses by measuring the total stellar luminosity
of the galaxies.
My favorite part of the course was our study of the Hertzsprung-Russell diagram--the graph of stellar luminosity
versus temperature that groups different types of stars and their developmental stages.
During the early 20th century astronomers Hertzsprung and Russel independently discovered a correlation between the stellar luminosity
(brightness corrected for distance) and spectral class.
But they have had only limited opportunities to observe long-term changes in stellar luminosity
Fifteen feet (4 1/2 meters) in diameter, the Atwood Sphere was perforated with 692 holes that mapped the principal stars and relied--like the cosmos of Anaximander--on exterior ambient light for stellar luminosity
Based on the relative populations of different stellar luminosity
classes, Stern finds it "statistically likely that all comets in the Oort cloud have been [heated] to 27 kelvins [-246|C] at least once, and that 20 to 40 percent of all Oort comets have experienced at least one episode of surface heating to 50 K [-223|C].
There must be some kind of deep-rooted instability which drives the stellar luminosity
to become super-Eddington," says Shaviv.