Artist's Illustration – Evaporating Planet HD 209458b
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.
This artist's illustration shows a dramatic close-up of the scorched extrasolar planet HD 209458b in its orbit only 4 million miles from its yellow, Sun-like star. The planet is a type of extrasolar planet known as a "hot Jupiter."
The planet's outer atmosphere is extended and heated so much by the searing heat from the nearby star that it starts to escape the planet's gravity. This huge envelope of evaporating hydrogen (shown in blue) resembles a comet with a tail trailing behind the planet. Astronomers estimate the amount of hydrogen gas escaping HD 209458b to be at least 10,000 tons per second, but possibly much more. Much of the planet may eventually disappear, leaving only a dense core.