Exoplanet 55 Cancri e May Be a Lava World

Posted on March 30, 2016

55 Cancri e as a lava planet

An international team of astronomers has found that exoplanet 55 Cancri e may be a lava world. The researchers, led by the University of Cambridge, say one half of the planet appears to be completely molten. The other half of the rocky planet is almost completely solid.

The astronomers used data from NASA's Spitzer Space Telescope to examine the planet which orbits a sun-like star about 40 light years away in the Cancer constellation. It has widely varying conditions on either side of the planet. One the hot side temperatures can reach 2500 degrees Celsius while temperatures cool to 1100 degrees on the other side.

The rocky exoplanet is classified as a "super Earth." It has eight times the mass of the Earth and is twice the Earth's size. It orbits very closely to its parent star. A year on the 55 Cancri e is just 18 hours long. The planet is also tidally locked to its parent star so it always shows the same face to its star. This gives the planet a permanent day and permanent night side.

Dr Brice-Olivier Demory of the University's Cavendish Laboratory, the paper's lead author, says in a statement, "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. We still don't know exactly what this planet is made of - it's still a riddle. These results are like adding another brick to the wall, but the exact nature of this planet is still not completely understood."

55 Cancri e was once thought to be covered in water or made of diamond. However, the latest data indicates it is a rocky lava planet. The day side of the planet is the hottest and the part of the planet believed to be molten.

Demory also says, "On the day side, the temperature is around 2500 degrees Celsius, while on the night side it's about 1100 degrees - that's a huge difference. We think that there could still be an atmosphere on the night side, but temperatures on the day side are so extreme that the atmosphere may have evaporated completely, meaning that heat is not being efficiently transferred, or transferred at all from the day side to the night side."

A research paper on 55 Cancri e as a lava world was published here in the journal, Nature. Here is an animation of the fiery exoplanet orbiting its star:



Photo: NASA/JPL-Caltech