
© NASA/JPL-CaltechThe exoplanet 209458b, located 150 light-years from Earth. [Artist's concept]
Dry atmospheres of three exoplanets challenge ideas of how planets form.
Scientists searching for worlds outside of the Solar System say that three such planets - distant gas giants that resemble Jupiter - are surprisingly dry.
The atmospheres of these exoplanets, known as 'hot Jupiters', contain
between one-tenth and one-thousandth water vapour than predicted, measurements from the Hubble Space Telescope show. The findings, published 24 July in
Astrophysical Journal Letters, are at odds with theories of how planets form.
The study re-analyses observations of the exoplanets HD 189733b, HD 209458b and WASP-12b, which are 20 - 270 parsecs (60 - 870 light years) away from Earth. As each exoplanet crossed in front of its host star, Hubble observed the spectrum of infrared light filtering through the planet's atmosphere. A team led by Nikku Madhusudhan, an astronomer at the University of Cambridge, UK, then used atmospheric models to determine the combination of elements that produced each planet's spectrum.
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