Astronomer finds evidence of exosolar planets

A. Sue Weisler Life on a planet ruled by two suns might be a little complicated

One aspect of Joel Kastner's research focuses on how planets form from gas and dust.

Life on a planet ruled by two suns might be a little complicated. Two sunrises, two sunsets. Twice the radiation field.

In a paper published in Astronomy and Astrophysics, astronomer Joel Kastner and his team suggest that planets might easily form around certain types of twin, or binary, star systems. A disk of molecules discovered orbiting a pair of twin young suns in the constellation Sagittarius strongly suggests that many such binary systems also host planets.

“We think the molecular gas orbiting these two stars almost literally represents ‘smoking gun’ evidence of recent or possibly ongoing ‘giant’ planet formation around the binary star system,” says Kastner, professor at the Chester F. Carlson Center for Imaging Science.

Kastner used the 30-meter radiotelescope operated by the Institut de Radio Astronomie Millimetrique to study radio molecular spectra emitted from the vicinity of the two stars, which lie about 210 light-years away from our solar system. The scientists found in large abundance raw materials for planet formation around the nearby stars, including circumstellar carbon monoxide and hydrogen cyanide, in the noxious gas cloud.

“In this case the stars are so close together, and the profile of the gas in terms of the types of molecules that are there is so much like the types of gaseous disks that we see around single stars, that it’s a real link between planets forming around single stars and planets forming around double stars,” he says.

Planets that have just formed around young stars might leave leftover gas, a potential clue for astronomers who hunt planets.

Recently, direct imaging of planets orbiting single stars irrefutably confirmed the existence of exosolar planets—those that orbit stars other than our sun. In the spring, Kastner hopes to use the Institut de Radio Astronomie Millimetrique to look for gas left over from the formation of the planets orbiting single stars.

Kastner hopes to compare the molecular profile in the gas remnants surrounding the single star with the gas composition surrounding the dual-star system.

Kastner encourages other scientists to look closely at the twin-star system to see if planets are forming around them.

“We really don’t have any idea right now about what kinds of planets form around double stars or even if planets can form around double stars,” Kastner says. “It’s theoretically possible, but I’m not aware of a single observation yet of a planet orbiting a double star. I hope someone will go looking soon, if they haven’t already.”


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