January 7, 2014
Storms As Big As Jupiter’s ‘Great Red Spot’ Found On Brown Dwarfs
[ Watch the Video: Torrential Storm Clouds On Brown Dwarfs ]
Lee Rannals for redOrbit.com - Your Universe Online
Most brown dwarfs may contain storms as big as Jupiter’s “Great Red Spot,” according to findings presented at the American Astronomical Society in Washington.
Brown dwarfs are a form of star, but lack the mass to fuse atoms continually to turn themselves into a full-fledged star. The celestial bodies are like a cross between a Jupiter-sized gas planet and a star. Astronomers using NASA's Spitzer Space Telescope believe that most brown dwarfs could have cloud cover and storms.
"As the brown dwarfs spin on their axis, the alternation of what we think are cloud-free and cloudy regions produces a periodic brightness variation that we can observe," Stanimir Metchev, of the University of Western Ontario, Canada, said in a statement. "These are signs of patchiness in the cloud cover."
These cloudy regions take the form of torrential storms, which could include winds, lightning and rain. Brown dwarfs are too hot to contain water, but scientists believe these clouds could be made up of hot sand, molten iron or salt.
The team used Spitzer to observe 44 brown dwarfs as they rotated on their axis for up to 20 hours. Past studies found that some brown dwarfs have turbulent weather, so the team thought they would find a small fraction of them that vary in brightness over time. However, they saw that half the brown dwarfs showed variations, indicating that potentially all brown dwarfs are filled with storms.
"We needed Spitzer to do this," said Metchev. "Spitzer is in space, above the thermal glow of the Earth's atmosphere, and it has the sensitivity required to see variations in the brown dwarfs' brightness."
The scientists also found that some of these cool stars rotate more slowly than previously measured. Astronomers previously believed that brown dwarfs sped up to very fast rotations when they formed, and this rotation didn’t wind down. However, the latest observations with Spitzer change this belief.
"We don't yet know why these particular brown dwarfs spin so slowly, but several interesting possibilities exist," Aren Heinze, of Stony Brook University, New York, said in a statement. "A brown dwarf that rotates slowly may have formed in an unusual way -- or it may even have been slowed down by the gravity of a yet-undiscovered planet in a close orbit around it."
Studying the weather on brown dwarfs could open up new windows into what weather is like on planets outside our solar system, which is harder to study due to the glare of their host stars.
“Brown dwarfs are weather laboratories for planets, and, according to the new results, those laboratories are everywhere,” NASA said in a statement.