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Alien Weather

April 7, 2016

At the equator of a planet known as HD 189733b, the weather forecast might go something like this: Hazy skies with a chance of showers of molten glass, high temperatures of almost 2,000 degrees, and winds from the west at more than 5,000 miles per hour.

That’s the picture pieced together from more than a decade of observations of the planet — a giant ball of gas just a couple of million miles from its parent star.

It’s one of several astronomical bodies beyond the solar system on which scientists have seen evidence of weather — winds, clouds, or both. Some of these objects are planets. Others are brown dwarfs — objects that are more massive than planets, but not big enough to shine as stars. And at least one is an actual star — a weak stellar ember that’s far fainter and cooler than the Sun.

The weather on HD 189733b was revealed by space telescopes. As the planet passes in front of its star, starlight filters through the planet’s atmosphere. That adds the “fingerprint” of the atmosphere to the starlight. From that, scientists found that a jet stream blows from east to west at the planet’s equator, at more than 5,000 miles per hour. The winds probably are created by the extreme difference in temperature between the planet’s dayside and its nightside.

The atmosphere also contains tiny grains of silicate. Under the heat of the nearby star, they may form liquid droplets that fall from the sky — a rain of molten glass.


Script by Damond Benningfield


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