A low-mass main-sequence star of spectral classes M and L. Red dwarf stars range from about 0.6 solar mass at class M0 down to 0.08 solar mass in cool M and warm L, below which the proton-proton chain cannot run. Lower-mass bodies are termed brown dwarfs. At the transition, within class L, the two are difficult to distinguish. Effective temperatures range from 3800 K (6400^°F) at class M0 down to 2000 K (3100^°F) at class L0, and absolute visual magnitudes from +9 to +20. Downward along the main sequence, red dwarfs produce progressively more radiation in the infrared. Bolometric corrections (which account for invisible radiation) range from −1.2 magnitudes to around −6, so luminosities range from about 0.05 down to 2 × 10⁻⁴ the solar luminosity. Radii range from about 0.5 to down 0.1 solar. Spectra become increasingly complex, with titanium oxide and neutral metals appearing at the warm end of class M, these and vanadium oxide appearing toward the cool end, and neutral metals and metal hydrides appearing in class L.