Back in 2009, astronomers discovered an exoplanet by the name of GJ 1214b orbiting a star some 40 light-years away, practically making it our neighbor in galactic terms. The planet orbits its star every 38 hours, which is part of the reason it was able to be discovered in the first place.
Planets orbiting other stars are spotted by carefully watching the amount of light reaching our telescopes. When a planet passes between us and the parent star, it blocks a little bit of the light, dimming the star’s appearance from our perspective. The faster the planet orbits, the more times it passes between us and its star, and the easier it is to detect its presence.
According to measurements, GJ 1214b was a super-Earth, meaning its size lies somewhere between that of Earth’s and Neptune’s, our solar systems next biggest planet after ours. That description is quite broad, however, seeing as how Neptune is 3.9 times bigger than Earth. And seeing as how no planets in our own solar system lie in that size range, scientists can only speculate what a super-Earth-sized planet is likely to look like.
Since the planet is in of an interesting size, not that far away and orbits its star so quickly, it was an excellent choice for further studies. Scientists took an even closer look at the planet by carefully analyzing the light reaching us after having passed through its atmosphere. Based on what bands of light make it through the atmosphere, researchers could guess what the atmosphere is made out of.
The preliminary results were inconclusive, most likely because there’s a crap-ton of clouds blocking our view. Naturally, this answer wasn’t precise enough, so we pointed Hubble at it.
The Hubble observations used 96 hours of telescope time spread over 11 months. This was the largest Hubble program ever devoted to studying a single exoplanet. And now the results are in.
The Hubble spectra revealed no chemical fingerprints whatsoever in the planet’s atmosphere. This allowed the astronomers to rule out cloud-free atmospheres made of water vapor, methane, nitrogen, carbon monoxide, or carbon dioxide. The best explanation for the new data is that there are high-altitude clouds in the atmosphere of the planet, though their composition is unknown. Models of super-Earth atmospheres predict clouds could be made out of potassium chloride or zinc sulfide at the scorching temperatures of 450 degrees Fahrenheit found on GJ 1214b.
“You would expect very different kinds of clouds to form than you would expect, say, on Earth,” said Laura Kriedberg, a graduate student at the University of Chicago and first author on the paper.
The launch of NASA’s next major space telescope, the 6.5 meter James Webb Space Telescope, later this decade should reveal more about such worlds, Kreidberg said. “Looking forward, JWST will be transformative,” she said. “The new capabilities of this telescope will allow us to peer through the clouds on planets like GJ 1214b. But more than that, it may open the door to studies of Earth-like planets around nearby stars.”
The study, “Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b,” was published in Nature by Laura Kreidberg, Jacob L. Bean, Jean-Michel Désert, Björn Benneke, Drake Deming, Kevin B. Stevenson, Sara Seager, Zachory Berta-Thompson, Andreas Seifahrt, and Derek Homeier.