An Etymological Dictionary of Astronomy and Astrophysics

The process whereby a → brown dwarf cools over time after the → deuterium burning phase, which lasts a few 10⁷ years. The → effective temperature and luminosity decrease depending on the mass, age, and → metallicity. Even though massive brown dwarfs may start out with star-like luminosity (≥ 10^-3→ solar luminosities), they progressively fade with age to the point where, after 0.5 Gyr all → substellar objects are less luminous than the dimmest, lowest mass stars. More explicitly, brown dwarfs may start as star-like objects hotter than 2200 K, with → M dwarf spectral types, and, as they get older, pass through the later and cooler L, T, and Y spectral types (→ L dwarf, → T dwarf, → Y dwarf).

See also: → brown; → dwarf; → cooling.