Ultra-cool companion helps reveal giant planetsAstronomers have found a brown dwarf that is more than 99% hydrogen and helium. Described as ultra-cool, it has a temperature of just 400 degrees Celsius and its discovery could be a key step forward in helping astronomers distinguish between brown dwarfs and giant planets.
Source: Ultra-cool companion helps reveal giant planets (http://www.sciencedaily.com/releases/2012/05/120510100052.htm)