Scientists have identified a record breaking brown dwarf (a star too small for nuclear fusion) with the ‘purest’ composition and the highest mass yet known. 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.
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.
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% 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.
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).