In Egyptian mythology, Osiris, lord of the underworld, was torn into 14 pieces by the god Seth. In our galaxy the planet Osiris is suffering a similar fate, being ripped apart by the furious heat of its parent star, known only as HD 209458. The Jupiter-size Osiris orbits just 4.3 million miles from the star, one-eighth Mercury’s distance from the sun. Researchers have found nearly 100 similar “hot Jupiters,” but Osiris is unique because it passes directly in front of its star as seen from Earth. Using the Hubble Space Telescope, astrophysicist Alfred Vidal-Madjar of the Institute for Astrophysics in Paris detected starlight streaming through the planet’s outer layers and determined that its atmosphere is boiling off, creating a large cloud.
The observations reveal the cloud contains carbon and oxygen—the first time anyone has found those life-critical compounds on a planet around another star. “Now that we’ve shown we can detect oxygen and carbon in the atmosphere of an extrasolar planet, we’re in a good position for finding a planet like Earth in the not too remote future,” Vidal-Madjar says. In 2006 the French Space Agency’s Corot spacecraft will look for other silhouetted planets that might reveal more about the composition of alien worlds.