Astro-weather forecast for alien super-Earth planet: Cloudy and hot

Astronomers observing a nearby alien world have produced what could be called the very first exoplanet weather forecast — cloudy and hot — and unlike their meteorologist counterparts forecasting for here on Earth, these 'extraterrestrial' forecasters can say with some certainty the forecast isn't going to change. Period.

GJ 1214b is a scorching hot alien world, roughly 40 light years away, that belongs to the class of planets called 'super-Earths' — so called because they are larger and more massive than the Earth, but smaller than the planet Neptune. Scientists are very interested in this class of planet, because they're completely new to us — there aren't any examples of them in our own solar system. They're also they're keen on figuring out where the lines get drawn between rocky worlds like Earth, ice giant planets like Neptune, and the possible 'water worlds' that could exist at sizes between those two.

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One way of figuring this out is to read what's in the planet's atmosphere. Using the Hubble Space Telescope, astronomers from the University of Chicago watched the tiny red dwarf star GJ 1214 as its super-Earth planet transited across its face every 38 hours. Every time the star's light dimmed, the astronomers gathered data about exactly how the light dimmed at different wavelengths of light. From that, they would be able to tell what molecules were present in the atmosphere to absorb the light at those wavelengths — a kind of chemical 'fingerprint.'

When the team examined the data they'd gathered, they were in for a bit of a surprise, though. Even though there are some 'typical' molecules that should be present in the atmosphere of a planet like GJ 1214b, the astronomers didn't see any of these chemical fingerprints. Measurements taken by another team of astronomers from Caltech, while looking at a 'warm Neptunian' planet called GJ 436b, showed a similar lack of chemical fingerprints. That team believes that this may be either due to clouds in the upper atmosphere or a denser atmosphere made from heavier molecules, which would make it more difficult to read. However, the University of Chicago team took such precise readings that they can rule out the possibility of the thicker atmosphere.

"What that means is that there must be clouds in the atmosphere blocking our view," Laura Kreidberg, the University of Chicago graduate student who led the study, said in a video presentation. She went on to say that the clouds on GJ 1214b wouldn't be like anything we've seen here on Earth. With the size and temperature of the planet, they could be composed of something like zinc sulfide or potassium chloride.

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According to the researchers, although they're impressed with the work they were able to do with the venerable Hubble Space Telescope, it's probably going to take the powers of NASA's James Web Space Telescope (due to launch in 2018) for them to revisit their work with GJ 1214b. They're also hopeful that the JWST will allow them to examine the atmospheres of even smaller exoplanets.

In the mean time, though, the discovery of Kreidberg and her colleagues now becomes the very first clear evidence of clouds in the atmosphere of a distant alien world.

(Images courtesy: NASA/ESA/A. Feild & G. Bacon (STScI))

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