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Astronomers Have Found The Most Massive Brown Dwarf Ever


Jonathan O'Callaghan

Senior Staff Writer

Artist's impression of the brown dwarf. John Pinfield

Astronomers have found the most massive brown dwarf we’ve ever seen, a failed star that has not started nuclear fusion at its core.

The object is called SDSS J0104+1535, and comes in at 90 times the mass of Jupiter. It was found by a team led by the Institute of Astrophysics in the Canary Islands using the Very Large Telescope (VLT) in Chile, and has been labelled an L type ultra-subdwarf. The finding was published in the Monthly Notices of the Royal Astronomical Society.


It’s located 750 light-years from Earth in the constellation of Pisces, found in a region of ancient stars in our galaxy. Interestingly, not only is it the most massive brown dwarf, but it’s also the “purest”. It’s composed of 99.99 percent hydrogen and helium, making it 250 times purer than the Sun, and has very little heavier elements in it like metals.

“We really didn’t expect to see brown dwarfs that are this pure,” Dr ZengHua Zhang of the Institute of Astrophysics in the Canary Islands said in a statement. “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 is thought to be about 10 billion years old, fairly early in our galaxy’s life, which itself took shape about 13.4 billion years ago. Being in a region of mostly primordial gas, it suggests that there are more brown dwarfs that have formed in our galaxy’s distant past.

Brown dwarfs are a rather peculiar intermediary between gas giant planets and small stars, most with a radius similar to Jupiter but a mass tens of times higher. We’re not quite sure yet what makes them different from each other, but continued studies could give us a bit more of an insight.


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