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HubbleSite Hubble Directly Measures Rotation of Cloudy 'Super-Jupiter'


Space Telescope Science

Though nearly 2,000 planets have been found around other stars, the light from only a handful of them has ever been collected by the world's most powerful telescopes. Ironically, a lot of them are detected by the shadows they cast, as they pass in front of their parent stars. Follow-up observations measure the planet's feeble, but telltale, gravitational tug on its parent star. Now, Hubble Space Telescope astronomers have been able to pick up the faint infrared glow of a giant planet located 170 light-years away from Earth. Not only is it glowing, but also rhythmically flickering as the planet spins on its axis like a top. The interpretation is that the subtle changes in the planet's brightness are due to a variegated cloud cover of comparatively bright and dark patches coming and going. These measurements have led to an estimate of how fast the planet is spinning through direct observation – a first for exoplanet astronomers. The gaseous world completes one rotation approximately every 10 hours, which, coincidentally, is the same rotation rate as Jupiter.

The planet is dubbed a "super-Jupiter" because it is four times the mass of Jupiter, the largest known planet in our solar system. Because the planet is a comparative newborn, it is still hot as it contracts under gravity. These characteristics allow for infrared observations. The planet orbits a faint brown dwarf, designated 2M1207. The dwarf is too small to shine as stars do through nuclear fusion. The dwarf is so dim and far from the planet astronomers were able to isolate the planet's glow.

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