Stormy stars? Spitzer probes weather on brown dwarfs

Jan 07, 2014
This artist's concept shows what the weather might look like on cool star-like bodies known as brown dwarfs. These giant balls of gas start out life like stars, but lack the mass to sustain nuclear fusion at their cores, and instead, fade and cool with time. Credit: NASA/JPL-Caltech/University of Western Ontario/Stony Brook University

(Phys.org) —Swirling, stormy clouds may be ever-present on cool celestial orbs called brown dwarfs. New observations from NASA's Spitzer Space Telescope suggest that most brown dwarfs are roiling with one or more planet-size storms akin to Jupiter's "Great Red Spot."

"As the 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," said Stanimir Metchev of the University of Western Ontario, Canada. "These are signs of patchiness in the cloud cover."

Metchev is principal investigator of the brown dwarf research. The results were presented at a news conference today at the 223rd annual meeting of the American Astronomical Society in Washington by Metchev's colleague, Aren Heinze, of Stony Brook University, New York.

Brown dwarfs form as stars do, but lack the mass to fuse atoms continually and blossom into full-fledged stars. They are, in some ways, the massive kin to Jupiter.

Scientists think that the cloudy regions on brown dwarfs take the form of torrential storms, accompanied by winds and, possibly, lightning more violent than that at Jupiter or any other planet in our solar system. However, the brown dwarfs studied so far are too hot for water rain; instead, astronomers believe the rain in these storms, like the clouds themselves, is made of hot sand, molten iron or salts.

In a Spitzer program named "Weather on Other Worlds," astronomers used the to watch 44 brown dwarfs as they rotated on their axis for up to 20 hours. Previous results had suggested that some brown dwarfs have turbulent weather, so the scientists had expected to see a small fraction vary in brightness over time. However, to their surprise, half of the brown dwarfs showed the variations. When you take into account that half of the objects would be oriented in such a way that their storms would be either hidden or always in view and unchanging, the results indicate that most, if not all, brown dwarfs are racked by 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 results led to another surprise as well. Some of the brown dwarfs rotated much more slowly than any previously measured, a finding that could not have been possible without Spitzer's long, uninterrupted observations from space. Astronomers had thought that brown dwarfs sped up to very fast rotations when they formed and contracted, and that this rotation didn't wind down with age.

"We don't yet know why these particular brown dwarfs spin so slowly, but several interesting possibilities exist," said Heinze. "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."

The work may lead to a better understanding of not just brown dwarfs but their "little brothers": the gas-giant planets. Researchers say that studying the weather on brown dwarfs will open new windows onto weather on planets outside our solar system, which are harder to study under the glare of their stars. Brown dwarfs are weather laboratories for planets, and, according to the new results, those laboratories are everywhere.

Explore further: Nearby failed stars may harbor planet

Related Stories

Nearby failed stars may harbor planet

Dec 16, 2013

(Phys.org) —Astronomers, including Carnegie's Yuri Beletsky, took precise measurements of the closest pair of failed stars to the Sun, which suggest that the system harbors a third, planetary-mass object.The ...

Drawing the line between stars and brown dwarfs

Dec 10, 2013

(Phys.org) —Stars come in a tremendous size range, from many tens of times bigger than the Sun to a tiny fraction of its size. But the answer to just how small an astronomical body can be, and still be ...

Brown dwarf companion stars

Sep 02, 2013

(Phys.org) —Astronomers trying to understand how the Sun and Earth formed, and why they have their characteristic properties, have made progress on a closely related problem: the nature of the lowest mass ...

The galaxy's ancient brown dwarf population revealed

Nov 20, 2013

(Phys.org) —A team of astronomers led by Dr David Pinfield at the University of Hertfordshire have discovered two of the oldest brown dwarfs in the Galaxy. These ancient objects are moving at speeds of ...

Recommended for you

Astronomers measure weight of galaxies, expansion of universe

7 hours ago

Astronomers at the University of British Columbia have collaborated with international researchers to calculate the precise mass of the Milky Way and Andromeda galaxies, dispelling the notion that the two galaxies have similar ...

Mysterious molecules in space

18 hours ago

Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum. Forged in the fusion furnaces of ancient stars and ejected into space when those stars ...

Comet Jacques makes a 'questionable' appearance

Jul 28, 2014

What an awesome photo! Italian amateur astronomer Rolando Ligustri nailed it earlier today using a remote telescope in New Mexico and wide-field 4-inch (106 mm) refractor. Currently the brightest comet in ...

Image: Our flocculent neighbour, the spiral galaxy M33

Jul 28, 2014

The spiral galaxy M33, also known as the Triangulum Galaxy, is one of our closest cosmic neighbours, just three million light-years away. Home to some forty billion stars, it is the third largest in the ...

Image: Chandra's view of the Tycho Supernova remnant

Jul 25, 2014

More than four centuries after Danish astronomer Tycho Brahe first observed the supernova that bears his name, the supernova remnant it created is now a bright source of X-rays. The supersonic expansion of ...

User comments : 0