An international team of researchers have found a record-breaking brown dwarf.
A brown dwarf is something that’s not quite a star, and not quite a planet; rather, they’re something in between. They’re usually significantly larger than planets, but not massive enough that full nuclear fusion of hydrogen to helium can take place inside them. Most brown dwarfs are only slightly larger than Jupiter (by 10% or so), but can be up to eighty times heavier because of significantly higher density. Now astronomers have found the largest, and purest brown dwarf yet, on the very edge of the galaxy.
The object, called SDSS J0104+1535, is in the constellation Pisces, some 750 light years away, in the ‘halo’, the outermost reaches of the Milky Way, where the oldest stars reside. The dwarf is made of 99.99% hydrogen and helium, which makes it chemically 250 times purer than our own Sun. The astronomers believe it was formed some ten billion years ago. It is also estimated to be some ninety times heavier than Jupiter, making it the most massive brown dwarf to date.
Before the discovery, scientists weren’t sure if brown dwarfs could form in such a a pure, primordial gas mixture, but now, astronomers realize there may be several other objects like it, floating out there in the dark. The research effort was headed by Dr ZengHua Zhang of the Institute of Astrophysics in the Canary Islands. He said: “We really 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.”
SDSS J0104+1535 has been classified as an L-type ultra-subdwarf based on a classification scheme only recently put in place by Dr. Zhang. The class can be identified partially through their red glow. The classification is based on observations of the dwarf in the visible and near infrared spectrum with the European Southern Observatory’s Very Large Telescope (VLT).
source: Royal Astronomical Society