Windy conditions are forecast for聽HAT-P-7b today, while聽heavy gem cloud may clear up later Mark Garlick/University of Warwick
It鈥檚 cloudy with a chance of gemstones. A super-sized planet 1000 light years from Earth has clouds that may contain the building blocks of rubies and sapphires, according to the first exoplanet meteorology report.
The planets in our solar system experience a wide variety of weather, from Jupiter鈥檚 famous Great Red Spot through Mars鈥檚 dust devils to Saturn鈥檚 hexagonal north polar storm. But planets around other stars are too distant for us to directly discern their short-term weather, such as changes in clouds or wind.
Now, at the University of Warwick, UK, and colleagues scrutinised four years of data from the Kepler satellite, and noticed that the brightness of a planet called HAT-P-7b changed over time.
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鈥淲ith this four-year timeline, you can really start to look in depth at these planets,鈥 says , who studies exoplanet atmospheres at the NASA Goddard Space Flight Center in Greenbelt, Maryland, and was not involved in the work. 鈥淥ur full understanding of these planets and the clouds in their atmospheres is just beginning.鈥
Vaporised minerals
The planet is about 40 per cent larger than Jupiter and is baked to a searing 2200 degrees kelvin (1900 掳C), in part because it鈥檚 so close to its star 鈥 it completes an orbit every two days. Armstrong and colleagues found the brightest areas on the planet moved around with time, which they say is due to changes in cloud coverage around the world.
The planet is locked in position, so it shows the same side to the star, the way the moon always displays the same face to Earth. As a result, the planet鈥檚 day side is much hotter than its night side. Clouds could condense on the cooler night side, and the temperature difference would create winds that send the clouds streaming around the planet.
鈥淭he winds transport clouds from the night side, so the cloud bank stretches some way into the day side before finally evaporating,鈥 Armstrong says. As the clouds evaporate, the planet absorbs more light and warms up, strengthening the winds.
鈥淲hen we say clouds, they鈥檙e definitely not clouds like on the Earth,鈥 Armstrong says. The planet is so hot that minerals would be vaporised.
Based on its boiling point, Armstrong says the clouds are likely made of corundum, the same mineral that produces sapphires and rubies on Earth. But more detail is needed to determine the clouds鈥 exact make-up.
Eventually, more powerful telescopes like the James Webb Space Telescope and the European Space Agency鈥檚 PLATO telescope will be able to study those clouds, and potentially search for signs of life in exoplanet atmospheres. But Wakeford says there鈥檚 plenty of exoplanet meteorology to do in the meantime.
鈥淢aybe in all the other stars that Kepler looked at, there is something else we haven鈥檛 quite discovered yet,鈥 she says.
Journal reference: Nature Astronomy, DOI: 10.1038/s41550-016-0004
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