Two teams of researchers using NASA’s Hubble Space Telescope report finding thick layers of high-altitude clouds in the atmospheres of two nearby exoplanets: a “warm” Neptune and a super-Earth.
The two planets are among the closest to our solar system found so far. The warm Neptune, classified as GJ 436b, is a relatively close 36 light years from Earth in the constellation Leo. The planet is slightly larger than our own Neptune and orbits much closer to its host star. And unlike the icy gas giant in our solar system, GJ 436b’s surface temperature is a blazing hot 980 degrees Fahrenheit.
The super-Earth, named GJ 1214b, has a radius 2.7 times that of Earth and is some 40 light years away in the constellation Ophiuchus. Super-Earths are planets with masses between that of Earth and Neptune. Because such planets aren’t found in our solar system, their physical characteristics are still largely a mystery.
“Super-Earth and Neptune-class planets collectively represent and intriguing and populous type of extrasolar planet whose exotic atmosphere may have no true analogies in the solar system,” wrote Julianne Moses of the Space Science Institute in Boulder, Colo. in a commentary on the two separate papers to be published Jan. 2 in the journal Nature, the LA Times reports. Moses was not involved in the studies.
Planets like GJ 436b and GJ 1214b can be observed as they pass in front of, or transit, their host stars. This gives scientists a chance to study the planets in more detail as starlight filters through their atmospheres, according to the authors. The researchers look for changes in certain wavelengths of light, which indicate what chemicals are in the atmosphere.
One research team, led by Heather Knutsen of the California Institute of Technology in Pasadena, Calif., studied the atmosphere of GJ 436b and was impressed not with what they found but with what they didn’t find. Hubble revealed “no chemical fingerprints whatsoever,” according to a HubbleSite news release.
The other team, led by Laura Kreidberg and Jacob Bean of the University of Chicago, found the same was true of super-Earth GJ 1214b. The researchers say the most likely reason for the absence of chemical signatures would be a thick layer of high-altitude clouds blocking the view.
Computer models of both exoplanets suggest the clouds could be made of potassium chloride or zinc sulfide. “You would expect to find very different kinds of clouds to form on these planets than you would find, say, on Earth,” Kreidberg noted.