astronomy: oxygen, carbon found on faraway planet

An international team of astronomers using the Hubble Space Telescope has found the first planet outside our solar system with detectable oxygen and carbon in its atmosphere. But the possibility of extraterrestrial life is pretty slim. Planet HD 209458b (nicknamed Osiris) is a hot Jupiter-like gas giant tightly orbiting a star 150 light-years away. The planet’s upper atmosphere is a fiery 18,000 degrees Fahrenheit. At such extreme temperatures, hydrogen atoms can escape the planet’s gravity at near sonic speeds, dragging heavier oxygen and carbon atoms with them, a phenomenon called “blow off.” It was the oxygen and carbon that the team detected. The combined gravitational fields of the star and planet stretch Osiris’s evaporating atmosphere into an elliptical shape. The discovery is to be reported in an upcoming issue of Astrophysical Journal Letters.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 2/10/2004.