STORMS have clouded Uranus鈥檚 normally placid face. In the past year, the gas planet has played host to huge cloud systems so bright that even amateur astronomers can see them from Earth 鈥� and their cause is a mystery.
鈥淲e have no idea. It鈥檚 very unexpected,鈥� says Imke de Pater at the University of California, Berkeley.
De Pater observed Uranus on 5 and 6 August, 2014, and was surprised to spot unusually bright features, the hallmark of clouds condensing in the planet鈥檚 upper atmosphere. 鈥淚t was brighter than anything we had ever seen in Uranus鈥檚 atmosphere before,鈥� she says. The planet鈥檚 weather generally picks up at its spring and autumn equinoxes every 42 years, when the sun shines on the equator. But the last equinox was 7 years ago, so the recent spike in activity is difficult to explain.
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De Pater鈥檚 group spread the word, and amateurs around the globe trained their telescopes on Uranus. Coincidentally, the amateurs spotted a storm that de Pater had imaged at a different wavelength on 5 August. Using the Hubble Space Telescope, de Pater and her colleagues saw storms spanning a variety of altitudes (), which could be linked to a vortex deep in Uranus鈥檚 atmosphere.
This article appeared in print under the headline 鈥淲hy the temper tantrum, Uranus?鈥�
