BROWN DWARFS: stars too small to perform nuclear fusion (no new energy) but too massive to be a planet

• Masses range from 13 Jupiter-masses to 25 Jupiter-masses
• Radius same as Jupiter but be up to 60-90 Jupiter masses
• Some emit x-rays
• All glow red in the infrared spectra until they cool off to 1,000 K

In 1995, the first brown dwarf, Teide 1 of the Pleiades cluster (M8 star), was discovered by the Spanish Observatory of Roque de los Muchachos and verified. Most brown dwarfs belong to spectral types L and T, which contain cooler stars than spectral type M. So far, more than 1,000 brown dwarfs have been discovered.