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Atmospheres Detected for Two Extrasolar Planets

Do extrasolar planets have water? In an attempt to find out, the orbiting Spitzer
Space Telescope made detailed observations of the atmospheres of two planets that
orbit stars other than our Sun. Unfortunately, water vapor was not detected in either
exoplanet. Spitzer watched star systems HD 209458b and HD 189733b closely in infrared
light both before and after the parent stars eclipsed their known planets. By comparing
eclipsed and uneclipsed spectra very closely, astronomers could deduce bright light-emitting
atmospheric gasses that were being blocked during eclipse. Were water vapor one of these
atmospheric gases, a new indication that life might exist outside of our Solar System would
have been found. The planets being analyzed are known as hot Jupiters -- they have sizes close
to Jupiter but orbits closer to the distance of Mercury. The above illustration shows an artist's
depiction of one of these dry worlds. Although no water vapor was detected this time, the
techniques of measuring exoplanet atmospheres are quite promising, and the search for distant
water and other biomarkers is just beginning.