LOS ANGELES — Some highly unusual planets orbiting other stars are calling into question current theories about how solar systems are formed and suggesting that more complex theories must be developed.
European researchers reported Tuesday that some of the recently observed extrasolar planets are revolving around their stars in the opposite direction from the stars’ spin.
That finding is inconsistent with the view that planets are formed by the condensation of dust from a disc surrounding a newly formed star.
Some other planets were found to have highly tilted orbits that are also at odds with conventional theory.
The findings also suggest that planets with such eccentric orbits would destroy any smaller, rocky planets, eliminating the chance that an Earth-like planet could be orbiting around that same star.
“This is a real bomb we are dropping into the field of exoplanets,” astronomer Amaury Triad of the Geneva Observatory, one of the authors of the report, said in a statement.
The new results imply that at least some of these massive planets — known as hot Jupiters because they orbit close to their suns — must reach their final orbits not through the familiar process of accumulation of dust, “but rather through the much more dramatic and exciting process of gravitational billiards,” astronomer Alan Boss of the Carnegie Institution of Washington said in an e-mail.
In such a billiards scenario, close encounters between planets orbiting the star would result in some planets getting sling-shotted into highly eccentric orbits, in some cases even backward (or retrograde) ones.
In the view of astronomer William J. Borucki of NASA’s Ames Research Laboratory in Mountain View, Calif., “What’s wonderful is that we can measure the direction of the orbit and compare it to the spin of the star. It’s something brand new, that we are able to do this.”
The results were reported at a Glasgow meeting of the Royal Astronomical Society by astronomer Andrew Cameron of the University of St. Andrews in Scotland.
