The following is an extract from our monthly Launchpad newsletter, in which resident space expert Leah Crane journeys through the solar system and beyond. You can sign up for Launchpad for free聽here.
Jupiter is enormous, and its storms are objectively monumental. The Great Red Spot, for example, contains the biggest storm in the solar system, big enough to fit Earth inside and with winds blowing at upwards of 600 kilometres per hour. That鈥檚 just the biggest one, though 鈥� all of the beautiful swirls and whorls on Jupiter are produced by powerful storms and winds interacting with one another. And on a planet that could fit more than 1300 Earths inside of it, there鈥檚 room for a lot of storms.
Of course, all that chaos and turbulence makes understanding Jupiter鈥檚 atmosphere and how the different layers act on one another extraordinarily difficult. Enter the James Webb Space Telescope. JWST has been able to capture what had always appeared as blurry hazes around Jupiter in stark detail, allowing astronomers to study them and track their propagation around the planet.
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These hazes turn out to be caused by a powerful jet stream more than 4800 kilometres wide, made up of winds that blow around 515 kilometres per hour. That鈥檚 faster than any wind that鈥檚 ever been measured on Earth. This stream sits above Jupiter鈥檚 clouds in an area that other telescopes have never been able to resolve. But examining it with JWST should be able to help astronomers figure out how these high-level phenomena affect the weather deeper within the atmosphere.
The Great Red Spot and the newly identified jet stream are pretty impressive, but if you want to kick things up a notch, let鈥檚 look at Jupiter-like planets that sit closer to their stars. These are aptly called 鈥渉ot Jupiters鈥�. The hottest Jupiter we know of is named KELT-9b. It鈥檚 about twice the size of Jupiter but much less dense. The distance between KELT-9b and its star is only about 3.5 per cent of the distance between Earth and the sun, and it takes less than 1.5 Earth days to orbit its star. This hot Jupiter is also tidally locked, so the same side of the planet always faces the star. All of this makes KELT-9b one really, really hot Jupiter.
On its day side, temperatures can reach 4327掳C (7820掳F), which is hotter than some stars. It鈥檚 so hot that molecules are broken into their constituent atoms, only reforming when they drift around to the night side.
Well, I say 鈥渄rift鈥�, but there鈥檚 probably not a whole lot of peaceful drifting around on hot Jupiters like KELT-9b. All that heat on one side powers winds of around 10 kilometres per second 鈥� that鈥檚 a little over one-third of the speed of Earth orbiting the sun. Astonishingly fast. The whole planet, and other hot Jupiters, is like a just-stirred cup of tea, with powerful currents and enormous storms everywhere. The night side is probably shrouded in exotic clouds of iron or other compounds created as all those broken molecules reform. The day side is too hot for clouds.
Worlds like this may seem impossibly different from anything in our own solar system, but gas giants do generally all share some traits. They have strange currents in the different layers of their atmospheres, and those currents all affect one another and each planet as a whole. Even detecting the winds or clouds on hot Jupiters is difficult because they are so far away. Luckily, we have a Jupiter of our own to study, and figuring out how its weather works is perhaps the most important step towards understanding these even-more-extreme worlds.
