Coolest Star Ever Detected

April 11, 2008 -- A dim, lonely, weakling star with the lowest stellar temperature yet recorded has been found just 40 light-years from Earth.

The brown dwarf star is between 15 and 30 times the mass of Jupiter and has a surface temperature of a mild 660 degrees Fahrenheit (350 Celsius) -- about the surface temperature of the planet Mercury at the equator and much cooler than the surface of Venus.

The spectacularly unspectacular object is of special interest because it falls right smack in the middle of the final frontier that divides mega-planets from the puniest stars. Stars in that realm theoretically qualify as an entirely new stellar type -- what's called a Y class dwarf.

"This would be the last spectral type between stars and planets," said stellar researcher Loic Albert of the Canada France Hawaii Telescope in Hawaii.

Albert is part of the team which identified the newfound coolest star, which is called CFBDS0059. Their paper on the discovery is accepted for publication in the journal Astronomy and Astrophysics.

Because they are so dim by nature, Y class dwarfs are very hard to find and identify. In fact no one has succeeded in positively identifying a Y class dwarf, Albert said.

"To the human eye it would be invisible, even in a telescope," Albert said.

That's because it's not quite hot enough to glow red -- like an electric stove element. Rather, it's just below the "red-hot" temperature, glowing in infrared light instead.

For that reason, the astronomers identified and studied CFBDS0059 with near-infrared and infrared instruments of the Canada France Hawaii and Gemini North telescopes in Hawaii and the European Southern Observatory's NTT telescope in Chile.