What's too big and hot to be a planet but too small and cool to be a star? It's what astronomers call a brown dwarf. Pictures from the Hubble Space Telescope now show one clearly for the first time, orbiting a faraway star.
"People have been looking very hard for one of these for more than 20 years," said astronomer Sam Durrance.
The brown dwarf may be 50 times more massive than Jupiter. Its temperature is about 1300ºF. Our sun is 7000ºF to 8000ºF.
A brown dwarf starts out as a star does, growing from hydrogen clouds. As a star gathers enough hydrogen, it ignites and burns brightly. But a smaller hydrogen mass heats up without igniting. It remains a hot superplanet with a smoky glow.