Sirius B: the first white dwarf understood (1910s)
In 1915, Walter Adams photographed the spectrum of Sirius B and found a hot star far too faint for its temperature. Astronomers realized a white dwarf packs roughly a solar mass into an Earth-sized volume.
Established the white dwarf class and forced a reckoning with extreme stellar density.
Led to the physics of degenerate matter and a fuller theory of stellar endpoints.
White dwarfs have a pattern of overturning assumptions about stars. The color study is the latest instance.
