Backwards alien planets challenge theories, page 1

Backwards alien planets challenge theories
Findings also have implications for likelihood of finding Earth-like planets
By
Space.com
updated 2:14 p.m. ET, Tues., April 13, 2010

Several extrasolar planets have been discovered to be orbiting backwards — that is, they revolve in the opposite direction that their host star rotates — challenging accepted ideas of how planets form, according to the astronomers who made the discovery.

"This is a real bomb we are dropping into the field of exoplanets," said team member Amaury Triaud, a Ph.D. student at the Geneva Observatory in Switzerland.

The team announced the discovery of nine new transiting exoplanets today at the annual meeting of the Royal Astronomical Society in Glasgow, Scotland. Transiting exoplanets are ones that were discovered as they passed in front of their host star from the perspective of Earth, causing a dip in the light coming from that star.

When the new results were combined with earlier observations of 18 other transiting planets, the astronomers were surprised to find that six out of that larger sample of 27 exoplanets were orbiting in the opposite direction of the rotation of their host star (called retrograde motion) —the exact reverse of our own solar system. Astronomers first discovered a backwards-orbiting exoplanet in August 2009.

The new finding suggests that astronomers might have to revise some aspects of planet formation.

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