A team of scientists has found a new planet which orbits the
wrong way around its host star. The planet, named WASP-17, and
orbiting a star 1000 light years away, was found by the UK’s
WASP project in collaboration with Geneva Observatory. The
discovery, which casts new light on how planetary systems form
and evolve, is being announced today (12th August) in a paper
submitted to Astrophysical Journal. Since planets form out of
the same swirling gas cloud that creates a star, they are
expected to orbit in the same direction that the star spins.
Graduate students David Anderson, of Keele University, and
Amaury Triaud, of Geneva Observatory, were surprised to find
that WASP-17 is orbiting the wrong way, making it the first
planet known to have a “retrograde” orbit. The likely
explanation is that WASP-17 was involved in a near collision
with another planet early in its history. WASP-17 appears to
have been the victim of a game of planetary billiards, flung
into its unusual orbit by a close encounter with a “big b