Coldest Star Found—No Hotter Than Fresh Coffee

Warning: The news you are about to enjoy is extremely hot—relatively speaking.

According to a new study, a star discovered 75 light-years away is no warmer than a freshly brewed cup of coffee.

Dubbed CFBDSIR 1458 10b, the star is what's called a brown dwarf. These oddball objects are often called failed stars, because they have starlike heat and chemical properties but don't have enough mass for the crush of gravity to ignite nuclear fusion at their cores.

With surface temperatures hovering around 206 degrees F (97 degrees C), the newfound star is the coldest brown dwarf seen to date. (Related: "Dimmest Stars in Universe Spotted?")

"Over the years there has been steady but slow progress in pushing the boundaries of finding the coldest stars," said study leader Michael Liu, an astronomer at the University of Hawaii.

"But with this latest discovery we have made a big leap forward—besting the previous record holder by at least 150 Kelvin [270 degrees F, or 150 degrees C]," he said.

Coldest Star May Have Watery Atmosphere?

With an estimated mass of only 6 to 15 times that of Jupiter, CFBDSIR 1458 10b is the smaller and dimmer member of a binary system in which two brown dwarfs are locked in close orbit.

Liu and his team spotted the pair's faint infrared signature using the W.M. Keck Observatory and the Canada-France-Hawaii Telescope, both on the summit of Mauna Kea in Hawaii.

The discovery is stretching our understanding of where to draw the line between what is a planet and what is a star, Lui added. (Related: "'Super Earth' May Really Be New Planet Type: Super-Io.")

For instance, although surface temperatures on our solar system's Jupiter sit around -236 degrees F (-149 degrees C), astronomers have found so-called hot Jupiters orbiting other stars with surface temperatures around 1,000 degrees F (538 degrees C).

In star terms, "this new object is so much colder than anything else seen that it now enters the regime where it may actually have an atmosphere with water clouds," Liu said. (Related: "First Proof of Wet 'Hot Jupiter' Outside Solar System.")

"The most exciting aspect of this finding is that we might be on the threshold of finding a new class of objects that blurs the line between gas-giant exoplanets and brown dwarf stars previously seen—something I think that is really surprising the astronomical community."

What's more, the new star may not hold its "coldest" title for long: Scientists with NASA's Spitzer Space Telescope are working to confirm an even cooler brown dwarf with possible surface temperatures dipping down to a balmy 86 degrees F (30 degrees C).

The coldest known star will be described in an upcoming issue of the Astrophysical Journal.