A huge newly discovered exoplanet appears to be orbiting in the wrong direction.
Instead of traveling around its host star in the same direction the star spins, like all other known planets, this black-sheep planet is orbiting backwards. Scientists think the renegade orb, named WASP-17, got flipped around during a near collision with another planet during its youth.
"Shakespeare said that two planets could no more occupy the same orbit than two kings could rule England," astrophysicist Coel Hellier of Keele University in the U.K. said in a press release. "WASP-17 shows that he was right."
Planets are born from the same ball of rotating gas that creates their parent star, which is why they usually orbit — and spin — in the same direction as their star. While WASP-17 is the first planet known to orbit backwards, some planets in our own solar system, such as Venus, are spinning backwards. Like WASP-17, Venus may have experienced some kind of collision during its early history, which flung it into an unusual spin.
Researchers at South African Astronomical Observatory discovered the new exoplanet 1,000 light years away from Earth. In addition to its surprising orbit, the exoplanet stands out because of its size: Only half the mass of Jupiter but twice its volume, the researchers claim WASP-17 is now the largest known planet.
Its bloated girth may have something to do with its odd orbit, as scientists think the planet's highly elliptical, retrograde orbit might have created extra-strong terrestrial tides, which cause planets to expand and contract. The constant stretching could have inflated WASP-17 to its current swollen size. "This planet is only as dense as expanded polystyrene," Hellier said. "Seventy times less dense than the planet we're standing on."
WASP-17 marks the 17th exoplanet discovered by the Wide Angle Search for Planets (WASP) project, conducted by eight universities in the U.K. Because exoplanets don't give off any light of their own and are usually obscured by their super-bright host stars, the scientists find exoplanets by scanning hundreds of thousands of stars, looking for the subtle dimming that occurs when a planet passes in front its parent star.
See Also:
- Kepler Shows Exoplanet Is Unlike Anything in Our Solar System ...
- Astronomers Find Hidden Exoplanet in Hubble's Dustbin
- Smallest Exoplanet Is Most Earth-like Yet
- Top 5 Most Extreme Exoplanets
- Astronomers Closer to Exoplanet 'Holy Grail'
Image: An artist's impression of two close extra-solar planets. KASI/CBNU/ARCSEC.
