Quite a few of the planets we’ve found outside our Solar System are hot Jupiters, large worlds that orbit extremely close to their star. Now scientists report the discovery of a particularly bizarre such planet.
Called CoRoT-2b, the planet is located 930 light-years from Earth. It takes just 1.7 Earth days to orbit its host star, orbiting so close (more than 10 times closer than Mercury does our Sun) that one side of the planet is probably tidally locked to the star – that means, due to the intense gravity, one side always faces it like the Moon does our planet.
So far we’ve studied the temperatures of nine similar planets, and found that the hottest part on all of them was at the point nearest to their star, or slightly to the east, as the strong winds near the equator would be blowing east and displace the hot spot.
CoRoT-2b is unusual, though, because researchers led by McGill University in Montreal, Canada found that the hot spot on this planet is actually west of its center, using data from NASA's Spitzer Space Telescope. This may suggest the planet has winds traveling in the opposite direction, which itself poses a number of new questions.
“Nature has thrown us a curveball,” Nicolas Cowan, a co-author on the study, said in a statement. “On this planet, the wind blows the wrong way.”
In their paper in Nature Astronomy, the team proposes a number of ideas for the weird planet. It might be that the planet is spinning so slowly that it rotates slower than it orbits, which would allow its winds to travel backwards, like Venus in our Solar System.
However, this would upend some of our ideas about hot Jupiters, namely that planets in such tight orbits should be tidally locked. If this one is rotating slower than it orbits, this means it isn’t locked.
Another idea is that the planet’s magnetic field is interacting with its atmosphere and causing the change in wind, which could give us a rare chance to study an exoplanet’s magnetic field. Or it could be that large clouds are covering the planet and obscuring our view slightly, although this wouldn’t fit in with our ideas on how atmospheres circulate on other worlds.
There’s definitely something odd going on here. While we don’t know for sure yet, CoRoT-2b highlights how weird and wonderful the universe can be.
“The westward offset of CoRoT-2b is another example that hot Jupiters are not all the same,” the researchers write.
“More broadly, each scenario outlined above challenges our understanding of short-period planets.”