stellar-physics

Spectroscopy, the analysis of light spread out by wavelength, is the most productive tool in astronomy. From a single beam of starlight it can reveal temperature, composition, speed, rotation, and magnetic field strength. Doppler shifts of spectral lines exposed the expansion of the universe, and the fingerprints of atoms identify every element the light has passed through.

Cataclysmic variables are close binary stars in which a white dwarf pulls gas off a companion. The result is outbursts that range from dwarf novae flaring every few weeks to classical novae that brighten by up to a million times. This article explains the physics, the period gap, and the famous systems.

Wolf-Rayet stars are massive, extremely hot stars that have blown away their outer layers in winds of thousands of kilometers per second. They show us the inside of a star, they seed space with dust and heavy elements, and many will end as supernovae or black holes.