Astronomers have detected water in the atmosphere of a planet outside our solar system for the first time. The finding, to be detailed in an upcoming issue of Astrophysical Journal, confirms previous theories that say water vapor should be present in the atmospheres of nearly all the known extrasolar planets.
HD209458b is a world well-known among planet hunters. In 1999, it became the first planet to be directly observed around a normal star outside our solar system and, a few years later, was the first exoplanet confirmed to have oxygen and carbon in its atmosphere.
HD209458b is separated from its star by only about 4 million miles (7 million kilometers)—about 100 times closer than Jupiter is to our Sun—and is so hot scientists think about it is losing about 10,000 tons of material every second as vented gas.