Planet-sized object as cool as Earth found

UNIVERSITY PARK, Pa., Oct. 20 (UPI) -- The Spitzer Space Telescope has captured images of the coldest companion object to be directly imaged outside our solar system, U.S. scientists say.

Penn State astronomy Professor Kevin Luhman said the planet-sized brown dwarf moving through space with a companion white dwarf star is as cool as Earth.

"This planet-like companion is the coldest object ever directly photographed outside our solar system," said Luhman, who led the discovery team. "Its mass is about the same as many of the known extra-solar planets -- about six to nine times the mass of Jupiter -- but in other ways it is more like a star.

"Essentially, what we have found is a very small star with an atmospheric temperature about cool as the Earth's."

A brown dwarf forms just like a star out of a massive cloud of dust and gas but its mass is not enough to ignite thermonuclear reactions in its core, resulting in a failed star that is very cool.