Number 251 (Story #2), December 7, 1995 by Phillip F. Schewe and Ben Stein THE COOLEST AND LOWEST-MASS BROWN DWARF yet has been discovered in the Lepus constellation by astronomers from Caltech and Johns Hopkins. Brown dwarfs are star-like objects which do not possess enough mass to sustain fusion reactions. They might vastly outnumber regular stars but are hard to spot because they're so dark. Indeed astronomers suspect that brown dwarfs lose whatever energy they may have produced within 100 million years. Therefore searches are conducted among nearby, relatively young stars. The newly discovered brown dwarf, a companion to star G1229, has an estimated mass 20-50 times that of Jupiter. Its temperature was deduced to be less than 1200 K because of the presence of methane in the object's spectrum; at higher temperatures carbon likes to form CO2, while at lower temperatures it prefers forming CH4. (T. Nakajima et al., Nature, 30 November 1995.)