AST 309 Chapter Notes - Chapter 1-2: Double Star, Binary Star, Semi-Major And Semi-Minor Axes
Document Summary
Brown dwarfs and other sub stellar bodies behave like giant planets, but most of them may form like stars. A cloud of gas and dust must start out cold for gravity to overcome the cloud"s thermal unrest. Once it collapses, the gas must get hot and dense enough to ignite hydrogen fusion in its core. Igniting fusion requires a ball of gas 75 times the mass of jupiter. Below that mass, and the object cools down for billions of years until vanishing from sight. Brown dwarfs are between stars and giant planets. They arise by means of surprisingly puny versions of the processes that create stars. A few years ago they existed only in theory. Gases like lithium and methane are destroyed by heat of genuine stars, but can persist in the cooler confines of brown-dwarf atmospheres. As brown dwarfs age, they look like hot planets rather than cool stars.
