Scientists using NASA's Spitzer Space Telescope have discovered and directly imaged a small brown dwarf star, 50 times the mass of Jupiter... The discovery concerns a class of the coldest brown dwarfs, called T dwarfs... Luhman's team also discovered a second brown dwarf that is smaller yet, about 20 times the mass of Jupiter, orbiting another star... could be the youngest T dwarf known, offering scientists a snapshot of early brown-dwarf development. The two T dwarfs are the first to be imaged by Spitzer... Spitzer also discovered a T dwarf that is floating through space by itelf rather than orbiting...