Astronomy

View from the Ground

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Science  19 Feb 2010:
Vol. 327, Issue 5968, pp. 923
DOI: 10.1126/science.327.5968.923-a
CREDIT: LYNETTE COOK/GEMINI OBSERVATORY

Over the past few years, space telescopes have enabled scientists to study the atmospheres of planets outside our solar system. Two studies now show that ground-based telescopes can also be put to this use. Swain et al. used NASA's Infrared Telescope Facility in Hawaii to collect spectra of HD 189733b, a hot Jupiter-like planet 63 light-years away from Earth. Water, carbon dioxide, and methane had been detected already in its atmosphere. The new ground-based observations suggest fluorescent emission from methane, similar to that detected from Jupiter, Saturn, and Titan; thus the atmosphere of this planet is more complex than previously thought. In a separate study, Janson et al. used the Very Large Telescope in Chile to acquire a spectrum of one of the three known giant planets orbiting around the star HR 8799. This planetary system, located 130 light-years from Earth, had been directly detected in images taken with the Keck and Gemini telescopes in 2008. Likewise, the spectrum of HR 8799c, a planet 10 times more massive than Jupiter, was obtained directly, without the need to rely on a transit to separate the light of the planet from that of the star. Current theoretical models cannot reproduce the spectrum of this planet, underscoring the limitations of our current understanding of exoplanetary atmospheres.

Nature 463, 637 (2010); Astrophys. J. 710, L35 (2010).

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