Located 750-light-years-away in the constellation of Pisces is a brown dwarf named SDSS J0104+1535 that astronomers say has the ‘purest’ composition and highest mass yet known for such a star.

Brown dwarfs can be pegged as celestial wonders pegged as intermediate between planets and fully-fledged stars. These stars do not have the necessary mass to support full nuclear fusion of hydrogen to helium; however, they have significantly higher mass than planets. Authors behind the study describe it as a member of the halo – the outermost reaches of our Galaxy that is made of some of the most ancient stars in the Universe.

This particular brown dwarf is made of gas that is around 250 times purer than the Sun consisting of more than 99.99 per cent hydrogen and helium. According to astronomers the age of this particular dwarf is about 10 billion years and has a mass equivalent to 90 times that of Jupiter, making it the most massive brown dwarf found to date. 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). This classification was based on a scheme very recently established by Dr ZengHua Zhang of the Institute of Astrophysics in the Canary Islands.

Astronomers weren’t aware 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.

The research team was led by Dr Zhang who says they didn’t expect to see brown dwarfs that are this pure.

“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”, Dr Zhang said.

The study describing the discovery has been published in Monthly Notices of the Royal Astronomical Society.