Two Satellites See an Evaporating Exoplanet

A solar flare that erupted at just the right time and direction could disrupt long-distance phone calls here on Earth, or make TV signals drops out for a while. But that?s nothing compared to the pummeling one exoplanet takes from its home star.

Thanks to a rare moment of synchronicity between the Hubble and Swift satellites, researchers at NASA recorded the first observed change in the atmosphere of a planet outside of our solar system. The planet, called HD 189733b, received a rather rude shock from its home star.

Scientists have been using Hubble to keep an eye on this Jupiter-like gas planet since 2010. The planet orbits a star that can be seen easily with just a pair of binoculars, making it an easy target for astronomers trying to understand planetary atmospheres. In September 2011, Hubble was set to record HD 189733b passing in front of its star (a transit). But eight hours before that transit happened, Swift?a satellite charged with searching for cosmic explosions?caught something unexpected. The star that the exoplanet orbits expelled a giant X-ray flare.

Eight hours after the flare, Hubble recorded the planet?s atmosphere evaporating from its super-heated poles at an extreme rate. Hydrogen was leaving the confines of the gas giant at more than 300,000 miles per hour, and every second another 1000 tons of gas shot out into space, giving the planet a comet-like tail.

If the Sun released that much radiation, our planet probably would make it through just fine. HD 189733b, however, is about 12 times closer to its star than Mercury is to ours. Even though its star is smaller than the sun, that tiny distance doesn?t give the planet much chance to evade a blast of radiation. Luckily for the planet, it?s so huge (14 percent larger than Jupiter) that even the trauma of a flare won?t deplete its atmosphere completely.

This research will be published in an upcoming issue of Astronomy & Astrophysics.

Source: http://www.popularmechanics.com/how-to/blog/satellites-team-up-to-see-evaporating-exoplanet-10128964?src=rss

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