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HubbleSite Too Close for Comfort: Hubble Discovers an Evaporating Planet


Space Telescope Science

Astronomers using NASA's Hubble Space Telescope have observed for the first time the atmosphere of a planet beyond our solar system evaporating into space. Most of the planet may eventually disappear, leaving only a dense core. The evaporating planet is a member of a type of planet called a "hot Jupiter," a giant gaseous planet that orbits very closely around its parent star, drawn to it like a moth to a flame. The scorched planet, called HD 209458b, orbits only 4 million miles (7 million kilometers) from its yellow, Sun-like star. The planet circles the parent star in a tight 3.5-day orbit. The Hubble observations reveal a hot and bloated hydrogen atmosphere, which is evaporating off the planet. This huge envelope of hydrogen resembles a comet with a tail trailing behind the planet.

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