Massive brown dwarf discovered 750 light years away

Scientists have identified a record breaking brown dwarf with the 'purest' composition that is about 90 times as massive as Jupiter, located 750 light years away in the outermost reaches of our galaxy.

Brown dwarfs are intermediate between planets and fully-fledged stars. 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.

The object, known as SDSS J0104+1535, is located 750 light years away in the constellation of Pisces, SDSS J0104+1535 is made of gas that is around 250 times purer than the Sun, so consists of more than 99.99 per cent hydrogen and helium.

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.

It was previously not known if brown dwarfs could form from such primordial gas, and the discovery points the way to a larger undiscovered population of extremely pure brown dwarfs from our Galaxy's ancient past.

"We really didn't expect to see brown dwarfs that are this pure," said ZengHua Zhang of the Institute of Astrophysics in the Canary Islands.

"Having found one though often suggests a much larger hitherto undiscovered population, I'd be very surprised if there aren't many more similar objects out there waiting to be found," said Zhang.

SDSS J0104+1535 has been classified as an L type ultra-subdwarf using its optical and near-infrared spectrum, measured using the European Southern Observatory's Very Large Telescope (VLT).

The findings were published in Monthly Notices of the Royal Astronomical Society.