Exoplanet 55 Cancri E May Have Vapor Rock Clouds, Molten Oceans

Exoplanet 55 Cancri e, dubbed a super-Earth, is no place anyone would want to live, as it has potential rock vapor, molten lava that flows like water, and unprecedented temperature differences, but it’s an important world for scientific study. Astronomers have recently finished the first heat map of the distant world, revealing incredible features, but also leaving many questions unanswered.

The planet 55 Cancri e is about 40 light years away, and, according to Scientific American, there’s nothing like it in our own solar system. It was discovered in 2004 and has a mass a little over eight-times that of Earth, which makes it the first “super-Earth” ever discovered. Gliese 876 d was discovered a year later. The exoplanet is the first of its kind to be discovered so close to its star — so close that a year on 55 Cancri e is just 2.8 days.

That proximity helps astronomers study the exoplanet, especially since it moves across the surface of its sun from our perspective here on Earth. Brice-Olivier Demory, astrophysicist at the University of Cambridge’s Cavendish Laboratory, explained that the combination of characteristics makes the exoplanet full of possibilities.

“We haven’t yet found any other planet that is this small and orbits so close to its parent star, and is relatively close to us, so 55 Cancri e offers lots of possibilities.”

For one, researchers were able to use the Hubble Telescope to analyze the super-Earth’s atmosphere earlier this year, finding traces of hydrogen and helium. It was the first time astronomers could study the atmosphere of an exoplanet, but there are still questions about the composition of that atmosphere. Even the composition of the planet itself is, as Demory explained, ” (is) still a riddle.”

What they do have now is a map of the planet’s thermal “phase curve,” the variations in its brightness as it goes revolves around a star. It’s published in Nature here.

Demory and a group of scientists spent 80 hours observing through the Spitzer Space Telescope Infrared Array Camera, and concluding that the exoplanet has the greatest temperature differences ever observed on a planet. The day-side reaches about 2,427 degrees Celsius, according to Gizmodo. The night-side is about 1,027 degrees Celsius.

Exoplanet 55 Cancri e doesn’t rotate like the Earth. It’s tidally locked with its star, so one side of the planet always faces the star and the other is always shrouded in darkness, which partially explains the difference. Still, there is evidence that something is distributing heat away from the day-time surface, especially the “substellar point” closest two the sun.

That leaves two possibilities, and they’re both extraordinary.

The first is there is an atmosphere full of vaporized rock clouds. If this strange atmosphere exists, then prevailing winds could recirculate at least some of the heat from the day-side of the exoplanet. The problem is, scientists don’t know how rock clouds would work.

“We need something funny that could be gaseous on the dayside yet still condense out on the nightside. We’ve looked, but so far we haven’t found any substance to fit these criteria.”

So instead, the another theory is favored — oceans of molten rock. On the day-side, the magma would flow like water around the exoplanet until it reaches the night-side, then cools until it finally becomes solid rock. The hypothesis has some saying 55 Cancri e is two-faced, one face liquid the other solid (albeit still incredibly hot).

In the end, the astronomers are limited by the small size of the exoplanet and lack of sophistication in the new efforts to study small distant worlds. Even the data itself might just be incorrect. Some might even wonder why studying a planet that is so distant from Earth, both in proximity and character, is worth long observation campaigns with Spitzer and the Hubble.

Caltech geoscientist and study co-author Vlada Stamenkovic, explained this research will one day help researchers look at planets more like Earth.

“But in order to understand Earth-like planets we have to somehow understand their chemistry and their interiors, which govern things important for life, like oceans and atmospheres. Partially molten planets like 55 Cancri e could let us learn more about what is inside them and how they are made.”

Exoplanet 55 Cancri e might be a hellish combination of molten and solid rock, but researching it might help astronomers find that planet humans would like to live on.

[Image credit: NASA/JPL-Caltech]