Water vapor detected in clear skies on Neptune-sized exoplanet

Sep 30, 2014

Photo credit: NASA/JPL-Caltech

By Amina Khan

Eureka! Astronomers say they’ve discovered clear skies and water vapor on a Neptune-sized exoplanet named HAT-P-11b — which, at roughly four times the Earth’s radius, is the smallest planet yet known to host water in its atmosphere.

The discovery, described in the journal Nature, marks a milestone for scientists seeking to learn whether even smaller planets in far-off solar systems have atmospheres comparable to Earth’s.

Finding exoplanets is difficult enough, but examining the molecular contents of their atmospheres is even harder. Scientists wait for the planets to pass in front of their stars and then examine the starlight that filters through the translucent gassy shell around the planet’s silhouette. If there’s water in that slim atmospheric lining, it will absorb certain wavelengths of the filtered light, leaving a chemical fingerprint that astronomers can identify.

It’s a process known as transmission spectroscopy, and it’s not easy work. Thus far, scientists have only been able to really probe the contents of the air around big planets, such as those the size of Jupiter, which are easier to spot and have wider, more extended atmospheres.


 

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4 comments on “Water vapor detected in clear skies on Neptune-sized exoplanet

  • @ OP – The discovery, described in the journal Nature, marks a milestone for scientists seeking to learn whether even smaller planets in far-off solar systems have atmospheres comparable to Earth’s.

    I would suspect that many which have stable atmospheres and are cool enough to retain volatiles, do have water. Water seems common in our Solar-System, and there are many second generation stars which probably have planets and comets, as part of the accretion process.



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  • Interesting in terms of what it suggests as to the probability of earth-like life on exoplanets.
    Amazing that the technology is precise enough to determine the presence of a specific vapour on a small object light-years away.

    The Khan article might have more authority if it did not use the term “air” as a synonym of atmosphere, and if it identified the star in question.
    Also, the picture is OK as an illustration of the kind of observation used for the analysis, but it should have been more clear that it is not a picture of HAT-P-11b — most likely it is the transit of Venus, observed last year.



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  • 3
    aquilacane says:

    The discovery, described in the journal Nature, marks a milestone for scientists seeking to learn whether even smaller planets in far-off solar systems have atmospheres comparable to Earth’s.

    It’s more of a “where” than “whether” question. Wondering if there are others is akin to a person wondering if anyone has a similar size nose that drips as much snot. Plenty!



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  • They put a description on the original article.

    This artist’s illustration shows Neptune-sized exoplanet HAT-P-11b.
    Astronomers report in the journal Nature that they have discovered
    water in its atmosphere. (NASA/JPL-Caltech)

    Brilliant bit of work though.



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