Article Posted on : - Apr 09, 2010

Artist’s impression of a brown dwarf with companion planet.

WASHINGTON (PTI): Astronomers have discovered the coolest and nearest brown dwarf to date nearly 10 light-years from the earth.

An international team headed by Philip Lucas from the University of Hertfordshire in UK found the brown dwarf or failed star -- UGPSJ0722-05 -- all by itself, floating through interstellar space.

"It was possibly formed there on its lonesome or kicked out of its host star system by an ancient gravitational game of stellar pinball," they said.

"This makes it the nearest brown dwarf and one of 10 nearest stellar objects to our solar system. Although its location isn't entirely unexpected as it is thought that the galaxy is stuffed full of these objects, the chemical composition of its atmosphere is a bit of a conundrum".

Lucas said, UGPSJ0722-05 appears to be the coolest ever discovered. It could have a surface temperature as low as 400 Kelvin, even cooler than the team's previous record of slightly below 500 K.

How it got there may not ever be known, but its close proximity allows astronomers to carry out detailed analysis of the object, Discovery Channel reported.

"Brown dwarfs are too small to initiate nuclear fusion in their cores for long periods so they're not stars, but they are distinct from planets too," he said.

Their interior has a convective motion of material, ensuring it is constantly being mixed up, preventing chemicals from settling -- chemical differentiation is a planetary trait. Therefore, brown dwarfs are often considered to be the "bridge" between the most massive planets -- Jupiter-like gas giants -- and the smallest stars.

As brown dwarfs are technically "failed stars," they are naturally very dim in visible wavelengths, but they do emit in infrared and radiation.