Scientists in a Spin Over Exoplanet Orbits
The discovery of nine new exoplanets - planets outside of our own solar system - has led to findings that experts say turn accepted planetary theory on its head.
Astronomers studying the movements of planets orbiting neighboring stars have found that the characteristics of exoplanets can differ markedly from those of planets orbiting our Sun.
It was observed that six out of a sample of 27 exoplanets had retrograde motion - orbiting in the direction opposite to the rotation of their host star.
That is the reverse of how our Solar System functions.
The team of scientists also detected that more than half of all the "hot Jupiters" (giant exoplanets with masses as large or greater than Jupiter's) travel on planes misaligned with the rotation axis of their parent stars.
"The new results really challenge the conventional wisdom that planets should always orbit in the same direction as their star's spin," said Professor Andrew Collier Cameron of the University of St Andrews
The new research is being presented today at the Royal Astronomical Society's National Astronomy Meeting in Glasgow.
These new discoveries challenge current theories of how planets form. Planets are believed to form amidst a proto-planetary disc of gas and dust circling a young star, rotating in the same direction as the star itself. The accepted theory is that planets forming from that disc would orbit on more or less the same plane, and move in the same direction as their star's rotation.
The findings also suggest that systems with "hot Jupiters" are not likely to contain Earth-like planets. Perhaps, the scientists suggest, the large planets migrated toward their host stars from other distant stars over hundreds of millions of years, rather than being formed from a common dust disc. Such gravitational tug-of-wars could swing the exoplanets into titled orbits.
"A dramatic side-effect of this process is that it would wipe out any other smaller Earth-like planet in these systems," said Didier Queloz of Geneva Observatory.
The new observations were made by astronomers in the Wide Angle Search for Planets (WASP), using European Southern Observatory facilities in Chile, France and the Canary Islands.
On Thursday the WASP consortium will receive the Royal Astronomical Society's 2010 Group Achievement Award.