A previously undetected element has been found in the atmospheres of two different extrasolar planets. Using a new technique at a new telescope, two separate groups of exoplanet scientists have discovered potassium in the atmospheres of two hot Jupiters more than 190 light-years from Earth.

“I’m really excited about this,” exoplanet expert Sara Seager of MIT, who was not involved in the new discoveries, said in an e-mail. “Together with other ground-based advances it is changing exoplanet atmosphere studies in a huge way.”

The two groups, one led by exoplanet scientist David Sing of the University of Exeter and the other led by University of Florida grad student Knicole Colón, used the 34-foot-wide Gran Telescopio Canarias in the Canary Islands to observe the planet XO-2b, located around 500 light-years from Earth, and the planet HD 80606b, about 190 light-years from Earth.

Both planets pass in front of their stars, or transit, from the vantage point of Earth. As the planet crosses its star’s face, some of the light from the star seeps through the glowing ring of the planet’s upper atmosphere. Different atoms and molecules interact with light in specific ways, so observing the light that makes it through the atmosphere allows scientists to figure out what elements it contains.

The two teams both used a new technique called narrowband transit spectrophotometry to focus in on potassium. Earlier studies of exoplanet atmospheres looked at all the light passing through the planet’s atmosphere, which restricted them to studying only the brightest stars. But Sing, Colón and their colleagues used a special filter that looks only at the particular wavelengths of light where potassium was expected to be found. The results are online at arXiv.org and will be published in two papers in Astronomy & Astrophysics and the Monthly Notices of the Royal Astronomical Society.

The new technique will eventually let astronomers measure the atmospheres of smaller planets around dimmer stars, says University of Florida exoplanet expert Eric Ford, a co-author of the paper describing HR 80606b.

“We can study these small planets, whether they’re mini-Neptunes or super-Earths, and answer some questions about them now, rather than waiting for next generation of big space telescopes,” he said.

These first two potassium-bearing planets are strikingly different. XO-2b is about the size of Jupiter, a little more than half Jupiter’s mass, and revolves sedately around its star once every 2.6 Earth days. Sing and his colleagues found a clear signature of potassium gas as a stable component of the planet’s atmosphere.

HD 80606b, on the other hand, is four times the mass of Jupiter and flies around its star in a crazy elliptical orbit that more closely resembles a comet’s orbit than a planet’s. The planet is flash heated as it comes close to its star, and then cools down again as it veers away. The atmospheric data suggests the potassium gas condenses into clouds when the planet is far from its star, and is being driven away from the planet by high-speed winds.

“They’re seeing a signature of that atmosphere being essentially boiled away as it goes by the star,” said exoplanet scientist Ruth Murray-Clay of Harvard, who was not involved in the new work. “It’s pretty extreme.”

Ultimately, astronomers would like to compare the amounts of several elements in the atmospheres of many different planets.

Seager and her colleagues predicted 10 years ago that potassium and sodium, both of which are solid on Earth, should be important gasses in most hot Jupiter atmospheres. But the first two planets to have their atmospheres analyzed showed only sodium.

The new discoveries “tell us that some of the basic models for hot Jupiter atmospheres that were proposed 10 years ago are pretty much right, in their gross characteristics,” Murray-Clay said. “It gives us some confidence that we have some idea of what’s going on, at least in the really hot ones.”

The fact that two potassium-bearing planets were announced on the same day indicates astronomers are moving into a new stage in exoplanet discoveries, Seager adds.

“Until now, in exoplanets, we’ve had interesting things that scratch the surface. You might find one molecule in one planet, or one new planetary system,” she said. “Now we’re on this watershed where all of a sudden, you could study 100 transiting planets with this technique. We’re moving into a much deeper level of work in exoplanets.”

Images: 1) ESA w/adaptations by David Sing. 2) The Gran Telescopio Canarias./Pablo Bonet.

See Also:

• Ground-Based Telescope Measures Exoplanet Atmosphere For First Time
• Most Earth-Like Extrasolar Planet Found Right Next Door
• Hubble Detects First Organic Molecule Around Exoplanet
• Life Ingredients Found on Extrasolar Gas Giant
• First Direct Measurement of an Exoplanet’s Light Spectrum

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Explosive bursts normally seen only on the surface of the sun can now be captured in a 13-foot-long tube using lab-created plasmas and bursts of laser light.

Physicists have created a scaled-down model of solar eruptions called coronal mass ejections, which can wreak havoc on satellites and create beautiful northern-light displays on Earth. The new experiments suggest these eruptions are set off when gushes of charged particles flow into twisted loops of magnetic field that extend from the sun’s upper atmosphere.

A magnetic flux arc in the lab.

“You can do things in the lab that are absolutely impossible to do in space,” said plasma physicist Walter Gekelman of the University of California, Los Angeles. Gekelman and UCLA physicist Shreekrishna Tripathi created miniature versions of enormous loops of solar matter called arched magnetic flux ropes. Their results are described in the Aug. 13 issue of Physical Review Letters.

These twisted magnetic ropes — also sometimes called coronal loops, prominences and filaments — can sit comfortably on the sun’s surface for hours or days, transporting energy and matter from the solar surface to the outer atmosphere. But eventually they explode, shooting tons of charged particles out into space like a slingshot. These loopy time bombs have been photographed by observatories like the Solar and Heliospheric Observatory — but how they form, and what makes them collapse, is still unknown.

“Astronomical observations give you pictures of things. It’s hard to deduce what’s going on inside of it,” said plasma physicist Steven Spangler of the University of Iowa, who was not involved in the new work. “So you’d really like to have a lab experiment to give you a scaled down version and bigger insights.”

Some theoretical models have suggested the eruptions are triggered by jets of plasma, or gas that is so hot that all the electrons have been stripped away from their parent atoms. These plasma jets are injected directly from the sun into the roots of the magnetic arcs.

To test this idea, the team of physicists used a cylindrical vacuum chamber about 13 feet long and 3 feet wide to hold a background plasma. Earlier experiments used a spark to create a plasma arc that simulated the solar loops, but without a background plasma, those loops fell apart too quickly to be realistic.

“Those conditions are very very different than in a real flux rope,” he said. “In the sun, there’s plasma everywhere, not just in the flux rope.”

Gekelman and Tripathi used two electromagnets to create an arched magnetic field, which produced a second plasma, analogous to the solar flux rope. They then fired two identical laser beams at carbon rods placed just behind the electromagnets, which shot two jets of carbon plasma directly into the ends of the flux rope.

These plasma jets created a destabilizing kink in the flux rope, making it erupt and send waves of energy rippling through the background plasma.

“They’re completely stable until we eject flow into them,” Gekelman said. “Then they go nuts.”

The experiment doesn’t absolutely prove plasma jets are responsible for coronal mass ejections, but “it’s a hint and an indicator and should stimulate additional research,” Spangler said. “We’re beginning to get some hints into what are the crucial ingredients.”

Image: 1) NASA/SOHO 2) S. Tripathi and W. Gekelman

See Also:

• 3-D Solar Tsunami Video Shows the Extreme Waves Are Real
• Sun’s Plasma Bursts Use Earth As “Magnetic Slingshot”
• Northern Lights’ Source Found in Giant “Magnetic Ropes”
• Video: The Butterfly Effect on the Sun’s Surface
• Video: Sun Puts on a Spectacular Eruption Show

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