An alien planet has winds that blow at 33,000 kilometres per hour

A vast alien planet has blistering winds racing around its equator at nearly 30 times the speed of sound on Earth.

Lisa Nortmann at the University of Göttingen, Germany and her colleagues used the European Southern Observatory’s Very Large Telescope in Chile to observe WASP-127b, a giant gas exoplanet more than 500 light years from Earth, which is slightly larger than Jupiter but one of the least dense known planets.

Nortmann and her team expected to see a light signal from the planet’s atmosphere that had one distinct peak, but instead found two separate peaks.

“I was a little bit confused,” says Nortmann. “But with a little bit more careful data analysis, it became clearer that there are two signals. I was quite excited – my first thought was immediately that it has to be some sort of super-rotating wind.”

The team concluded that the two peaks came from rapid winds in a jet stream around the planet’s equator, with half the wind moving towards Earth and the other half moving away from it. The wind, which appears to be made up of water and carbon monoxide, seems to be moving at 33,000 kilometres per hour, which makes it the fastest wind ever measured on a planet.

“We’re talking about 9 kilometres per second. The wind speed on even Jupiter is like a few hundred metres per second, so this is really an order of magnitude larger,” says Vivien Parmentier at the University of Oxford.

You wouldn’t be able to feel these extreme speeds if you were in this wind, because it would all be moving around you at the same speed, says Parmentier. But you would experience temperature differences of hundreds of degrees over a matter of hours, as the winds move from the hot side of the planet, which is permanently facing its star, to its cold side, which sits in constant darkness.

Nortmann and her colleagues don’t know why the planet has such extreme winds, but she says it has certain special properties, such as its low density and a wonky orbit around its star, that could play a role. “However, no clear connection has been established between those facts and the particularly strong winds,” says Nortmann.