“The brown dwarfs jump out at you like big, fat, green emeralds,” said Amy Mainzer, the deputy project scientist of WISE at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs appear like green gems in WISE images because the methane in their atmospheres absorbs the infrared light that has been coded blue, and because they are too faint to give off the infrared light that is color-coded red. The only color left is green.
Like Jupiter, brown dwarfs are made up of gas — a lot of it in the form of methane, hydrogen sulfide, and ammonia. These gases would be deadly to humans at the concentrations found around brown dwarfs. And they wouldn’t exactly smell pretty.
“If you could bottle up a gallon of this object’s atmosphere and bring it back to Earth, smelling it wouldn’t kill you, but it would stink pretty badly — like rotten eggs with a hint of ammonia,” said Mainzer.