April 13, 2010

New Planets Displaying Opposite Orbital Patterns

Astronomers have discovered nine new transiting exoplanets, some of which were found to orbit in the opposite direction as their host stars, according to a press release sent out by the Royal Astronomical Society (RAS) and the European Southern Observatory (ESO) on Tuesday.

The new exoplanets, when combined with others previously discovered by astronomers, brings to a total of 27, six of which were found to have the exact opposite orbital patterns of planets in our own solar system.

According to the press release, "The new discoveries provide an unexpected and serious challenge to current theories of planet formation. They also suggest that systems with exoplanets of the type known as hot Jupiters are unlikely to contain Earth-like planets."

The findings were presented by University of St. Andrews Professor Andrew Collier Cameron during the RAS National Astronomy Meeting (NAM 2010) at the University of Glasgow on April 13.

"To account for the new retrograde exoplanets an alternative migration theory suggests that the proximity of hot Jupiters to their stars is not due to interactions with the dust disc at all, but to a slower evolution process involving a gravitational tug-of-war with more distant planetary or stellar companions over hundreds of millions of years," wrote Dr. Robert Massey on the official RAS website.

"After these disturbances have bounced a giant exoplanet into a tilted and elongated orbit it would suffer tidal friction, losing energy every time it swung close to the star. It would eventually become parked in a near circular, but randomly tilted, orbit close to the star," he added.

NAM 2010 started on April 12 and will run until April 16.


Image Caption: Up to now it was expected that exoplanets would all orbit in more or less the same plane, and that they would move along their orbits in the same direction as the star's rotation "” as they do in our Solar System. However, new results unexpectedly show that many exoplanets actually orbit at a large angle to their star's spin axis. In the case shown here (WASP 8b) the orbit is completely reversed, or retrograde. Credit: ESO/L. Calçada


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