Wrong-way planets are a surprise

A UK-led planet hunt using equipment sourced via eBay has found nine new worlds around other stars. They bring the total number of discoveries by the SuperWASP project since 2006 to 28.

An exoplanet in transit

Intriguingly, two of the new planets are going round their parent stars the wrong way – orbiting in the opposite direction to that in which the star is spinning.

The finds present a serious challenge to current theories of how planets form, Professor Andrew Collier Cameron told the National Astronomy Meeting at Glasgow.

Stars and their families of planets like our own solar system are thought to form when vast clouds of gas and dust rotate and condense.

But more than half of the giant planets in close orbits – so-called “hot Jupiters” – have peculiar orbits which are out of line. One planet orbiting the wrong way hit the headlines in August last year.

The team believe the hot Jupiters end up in their close orbits after bizarrely richocheting around over many aeons thanks to the gravitational pull of a second companion star in the system.

Professor Cameron, of St Andrew’s University, Scotland, said: “The new results really challenge the conventional wisdom that planets should always orbit in the same direction as their star’s spin. It is a gravitational tug-of-war – a complete game of cosmic pinball over many millions of years.”

The planet ends up parked in a near-circular but randomly tilted orbit close to its parent star. But its dramatic journey to get there is bad news for any worlds like Earth.

Astronomer Didier Queloz, of Geneva Observatory, who helped confirm the WASP planets, said: “A dramatic side-effect of this process is that it would wipe out any other smaller Earth-like planet in these systems.”

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The SuperWASP project – short for Super Wide Angle Search for Planets – uses two banks of eight cameras, one in the Canary Islands and one in South Africa, to monitor millions of stars a night. It detects giant planets by spotting a small dip in light as they pass in front of the star.

Astronomers had to turn to auction site eBay to track down 13 lenses, costing £4,000 each, after they learned that Canon no longer made them.

Each observatory is kitted out with the specially-built digital cameras which cost £30,000 each and were made by Andor Technology in Belfast. Together they cover an area of sky 250 times the size of the Full Moon.

Smaller Earth-sized worlds will have to wait to be found by  other methods such as Europe’s Corot satellite and NASA’s Kepler space telescope.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available.

By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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