These results show just how challenging it could be to detect water on Earth-like exoplanets in our search for potential life elsewhere.
- Nikku Madhusudhan
A team of astronomers using NASA’s Hubble Space Telescope have gone looking for water vapour in the atmospheres of three planets orbiting stars similar to the Sun – and have come up nearly dry.
The three planets, HD 189733b, HD 209458b, and WASP-12b, are between 60 and 900 light-years away, and are all gas giants known as ‘hot Jupiters.’ These worlds are so hot, with temperatures between 900 to 2200 degrees Celsius, that they are ideal candidates for detecting water vapour in their atmospheres.
However, the three planets have only one-tenth to one-thousandth the amount of water predicted by standard planet formation theories. The best water measurement, for the planet HD 209458b, was between 4 and 24 parts per million. The results raise new questions about how exoplanets form and highlight the challenges in searching for water on Earth-like exoplanets in the future. The findings are published this week in the journal Astrophysical Journal Letters.
“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside the solar system, and we can now say with much greater certainty than ever before that we’ve found water in an exoplanet,” said Dr Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, who led the research. “However, the low water abundance we are finding is quite astonishing.”
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Image: Illustration of a 'hot Jupiter' orbiting a sun-like star
Credit: Haven Giguere, Nikku Madhusudhan
Reproduced courtesy of the University of Cambridge
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