Coldest-ever Star

Astronomers have located a planet-like star that’s barely warmer than a balmy summer day on Earth… it’s literally the coldest object ever directly imaged outside of our solar system!

An artist’s impression of the coldest imaged companion, named WD 0806-661 B, (right foreground) orbiting at a large distance from a white dwarf –the collapsed-core remnant of a dying star. Credit: NASA Goddard Space Flight Center/Francis Reddy



The photo of a nearby star and its orbiting companion — whose temperature is like a hot summer day in Arizona — will be presented by Penn State Associate Professor of Astronomy and Astrophysics Kevin Luhman during the Signposts of Planets conference at NASA’s Goddard Space Flight Center on 20 October 2011.

A paper describing the discovery will be published in the Astrophysical Journal. “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.”

Coldest-ever Star

A second artist’s impression of the coldest imaged companion, named WD 0806-661 B, (left foreground) orbiting at a large distance from a white dwarf — the collapsed-core remnant of a dying star. Credit: Janella Williams



Luhman classifies this object as a “brown dwarf,” an object that formed just like a star out of a massive cloud of dust and gas. But the mass that a brown dwarf accumulates is not enough to ignite thermonuclear reactions in its core, resulting in a failed star that is very cool. In the case of the new brown dwarf, the scientists have gauged the temperature of its surface to be between 80 and 160 degrees Fahrenheit — possibly as cool as a human.

Coldest-ever Star

Ever since brown dwarfs first were discovered in 1995, astronomers have been trying to find new record holders for the coldest brown dwarfs because these objects are valuable as laboratories for studying the atmospheres of planets with Earth-like temperatures outside our solar system.

science.psu.edu