An artist's portrayal of the "hot Jupiter" orbiting just 3 million miles from the star HD 189733. [ESA / NASA / M. Kornmesser / STScI]
Posted on 12/13/2008 6:36:55 PM PST by SunkenCiv
Discovered in 2005 using Doppler spectroscopy, HD 189733b is a"hot Jupiter" that circles just 3 million miles (0.03 astronomical unit) from its host star. This means it's hopelessly too close to its sun to be spotted separately with current technology. However, by good fortune, it is a transiting exoplanet that alternately passes in front of and behind its sun every 2.2 days. Recently astronomers have cleverly exploited this geometry to learn something about the Jupiter-size world's composition. First they record the combined spectrum of the star and planet together -- and then, once HD 189733b has ducked from view, that of the star alone... This week two teams of astronomers report, based on infrared spectra taken with both the Hubble and Spitzer space observatories, that there must be water on HD 189733b... its surface temperature near 2,500°F (1,400°C)... What's more puzzling is the signature of carbon dioxide there too. So I asked exoplanet expert Sara Seager (MIT) what she makes of this result. "The apparent detection of CO2 is very surprising," she told me, because it wouldn't be present if all of HD 189733b's gases were in chemical balance. "We think it comes from photochemistry, caused by the star's ultraviolet rays breaking up molecules that then reform as different molecules."
(Excerpt) Read more at skyandtelescope.com ...
An artist's portrayal of the "hot Jupiter" orbiting just 3 million miles from the star HD 189733. [ESA / NASA / M. Kornmesser / STScI]
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