Wednesday, September 24, 2014

Astronomers Can Now Detect Water on Exoplanets That Are Light Years Away

Water is the magic ingredient for life as we know it, and detecting it on Earthlike exoplanets is the best strategy for rooting out habitable worlds. Well, researchers at the University of Maryland have just detected water vapor in the atmosphere of an exoplanet 124 light years away.

That's huge for a couple reasons. For one, it's always good news for those searching for extraterrestrial life when they find water on another planet (in this case, the exoplanet HAT P-11b). For two, we now have the means of detecting water vapor that's light years away.

The planet is four times times bigger than Earth and boasts about 26 times its mass, making it roughly the size of Neptune. That might seem big, but HAT P-11b is actually the smallest exoplanet astronomers have ever found to be hosting water vapor. In fact, it’s the smallest world for which the atmospheric conditions have been discovered at all, making it a key step towards finding water on even smaller terrestrial exoplanets resembling Earth.

“The atmosphere [of HAT P-11b] is mostly molecular hydrogen, with an admixture of heavier molecules including water vapor,” Drake Deming, co-author of a paper describing the discovery in Nature told me, adding that only water vapor was directly detected. 

“The presence of molecular hydrogen is strongly inferred,” he explained. “Without hydrogen, the atmosphere would be too ‘compact’ to detect anything, [because] hydrogen reduces the mean molecular weight and allows the atmosphere to puff upward to the point where it blocks enough starlight for a detection.” 

The planet’s atmosphere may also contain methane, but Deming’s team needs more data to substantiate its presence.

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