brown dwarf star
March 29, 2017

Scientists discover biggest ever brown dwarf star

An international team of scientists has discovered a brown dwarf with the 'purest' composition and the greatest mass to date, according to a report in Monthly Notices of the Royal Astronomical Society.

The object, referred to as SDSS J0104+1535, is located in the outermost regions of our Galaxy, which is comprised of the oldest stars.

Brown dwarfs are somewhere between planets and stars. Their size is too little for complete nuclear fusion of hydrogen to helium to occur, but they are generally much bigger than planets.

While Jupiter might be thought of as a good analogy for a brown dwarf, a brown dwarf is actually warmer than the giant gas planet. The heat of a brown dwarf doesn’t come from fusion, but rather from gravity.

If a fixed quantity of gas gets compressed into a tight space, it gets warmer: This effect can be felt when inflating a tire. For Jupiter and a brown dwarf, gravity is consistently smashing the gas down, until some pressure resists it. This compression of the gas drives up the temperature of the gas in the brown dwarf, the hottest of which can get as warm as a standard operating kitchen oven.

Giant Made of Hydrogen and Helium

Situated in the constellation of Pisces, SDSS J0104 1535 is made from gas that is around 250 times purer than the Sun, greater than 99.99% hydrogen and helium. Believed to have developed approximately 10 billion years ago, observations in the study suggest it has a mass equal to 90 times that of Jupiter, which makes it the biggest brown dwarf ever discovered.

Astronomers haven't known if brown dwarfs could develop from such a composition and the finding indicates the possibility of a bigger unknown population of incredibly pure and very old brown dwarfs.

“We really didn't expect to see brown dwarfs that are this pure,” study author 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."


Image credit: NASA JPL