Using the Hubble Space Telescope, NASA astronomers have for the first time in history, successfully detected and analyzed the atmosphere of a planet outside the Earth's solar system. The breakthrough, says NASA, proves that telescopes can be used to search the atmospheres of extrasolar planets for the chemical markers of life.

The Jupiter-sized planet orbits a Sun-like yellow star called HD 209458 located some 150 light-years from earth in the constellation Pegasus. In order to probe the planet's atmosphere, NASA waited until its orbit brought it between its parent star and the Hubble Space Telescope. Astronomers were then able to study the light from the star as filtered through the planet's atmosphere. Hubble's onboard spectrometer detected the presence of sodium gas in the planet's atmosphere.

"This opens up an exciting new phase of extrasolar planet exploration, where we can begin to compare and contrast the atmospheres of planets around other stars," stated lead investigator David Charbonneau.

NASA astronomers determined that the planet was hot, probably too hot to sustain life. While Hubble's instruments were not tuned to look specifically for life-sustaining gases, this unique observing technique opens a new phase in the exploration of extrasolar plants, say astronomers. Such observations could potentially provide the first direct evidence for life beyond Earth by identifying large quantities of atmospheric gases, such as carbon dioxide, generated by living organisms.

First discovered in 1999, the planet is about 70 percent the size and mass of Jupiter, or about 220 times larger than the Earth. Of the approximately 80 extrasolar planets discovered to date, this one is the best for atmospheric study, according to NASA. The planet "transits" or passes between the Hubble telescope and its parent star every 3.5 Earth-days, thus offering more frequent opportunities for observation than the other distant planets.

Observations by Hubble and Earth-based telescopes confirmed that the planet is primarily gaseous, rather than liquid or solid, meaning that the planet is a gas giant, like Jupiter and Saturn.

Once NASA fine-tunes Hubble's instruments, astronomers hope to detect methane, water vapor, potassium and other chemicals in the planet's atmosphere.