Record-breaking brown dwarf is 'purest' and most massive

The dwarf is estimated to have formed about 10 billion years ago, measurements also suggest it has a mass equivalent to 90 times that of Jupiter, making it the most massive brown dwarf found to date.

London, Mar 25: Astronomers have identified a record-breaking brown dwarf - a star too small for nuclear fusion - with the 'purest' composition and the highest mass yet known, located 750 light years away. The object, known as SDSS J0104+1535, is a member of the so-called halo -- the outermost reaches -- of our galaxy, made up of the most ancient stars

It is located 750 light years away in the constellation of Pisces and is made of gas that is around 250 times purer than the Sun and consists of more than 99.99 per cent hydrogen and helium, researchers said.

The dwarf is estimated to have formed about 10 billion years ago, measurements also suggest it has a mass equivalent to 90 times that of Jupiter, making it the most massive brown dwarf found to date.

Intermediate between planets and fully-fledged stars

"We really did not expect to see brown dwarfs that are this pure. Having found one though often suggests a much larger hitherto undiscovered population -- I would be very surprised if there are not many more similar objects out there waiting to be found," said ZengHua Zhang of the Institute of Astrophysics in the Canary Islands, a Spanish archipelago off the coast of northwestern Africa. Brown dwarfs are intermediate between planets and fully-fledged stars.

Significantly more massive than planets

Their mass is too small for full nuclear fusion of hydrogen to helium (with a consequent release of energy) to take place, but they are usually significantly more massive than planets, researchers said.

The finding was published in the journal Monthly Notices of the Royal Astronomical Society.

Not discovered until 1995

Brown dwarfs are failed stars about the size of Jupiter, with a much larger mass but not quite large enough to become stars. Like the sun and Jupiter, they are composed mainly of hydrogen gas, perhaps with swirling cloud belts. Unlike the sun, they have no internal energy source and emit almost no visible light.

Brown dwarfs are formed along with stars by the contraction of gases and dust in the interstellar medium, McLean said. The first brown dwarf was not discovered until 1995.

'The 'desert' is not as dry as we think'

"We want to understand how brown dwarfs form around stars, and why there is a gap in where they are found relative to their host stars," said Yossi Shvartzvald, a NASA postdoctoral fellow based at NASA's Jet Propulsion Laboratory, Pasadena, California, and lead author of a study published in the Astrophysical Journal. "It's possible that the 'desert' is not as dry as we think."