A red dwarf is a small and relatively cool #star
on the main sequence, of either K or M #spectral
type. Red dwarfs range in mass from a low of 0.075 to about 0.50 solar mass and have a surface #temperature
of less than 4,000 K.
Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighborhood of the #Sun,
but because of their low luminosity, individual red dwarfs cannot be easily observed. From #Earth,
not one is visible to the naked eye. #Proxima #Centauri,
the nearest star to the Sun, is a red dwarf (Type M5, apparent magnitude 11.05), as are fifty of the sixty nearest stars. According to some estimates, red dwarfs make up three-quarters of the stars in the Milky Way.
Stellar models indicate that red dwarfs less than 0.35 M☉ are fully convective. Hence the helium produced by the thermonuclear fusion of hydrogen is constantly remixed throughout the star, avoiding helium buildup at the core, thereby prolonging the period of fusion. Red dwarfs therefore develop very slowly, maintaining a constant luminosity and spectral type for trillions of years, until their fuel is depleted. Because of the comparatively short age of the universe, no red dwarfs exist at advanced stages of #evolution.
#exoplanet #nasa #space #hubble #hubblespacetelescope #spacetelescope #telescope #universe #galaxy #solarsystem #astrophysics #picoftheday #galaxies #astronomy #science.