A planet, nicknamed the "diamond planet," has caught the attention of astronomers, mostly due to the mysterious rocky planet's temperature fluctuations. A threefold change in temperature over a two year period has been observed on 55 Cancri e, which orbits the sun-like star 55 Cancri A.
Researchers, led by the University of Cambridge, are quick to point out that the cause of the variability is still under investigation. They believe the readings could be due to massive amounts of volcanic activity on the surface. The ability to peek into the atmospheres of rocky "super-Earths" and observe conditions on their surfaces marks an important milestone towards identifying habitable planets outside the solar system.
"This is the first time we've seen such drastic changes in light emitted from an exoplanet, which is particularly remarkable for a super-Earth," said study coauthor Nikku Madhusudhan of Cambridge's Institute of Astronomy, according to a press release. "No signature of thermal emissions or surface activity has ever been detected for any other super-Earth to date."
Although the interpretations of the new data are still preliminary, the researchers believe the variability in temperature could be due to huge plumes of gas and dust which occasionally blanket the surface, which may be partially molten. The plumes could be caused by exceptionally high rates of volcanic activity, higher than what has been observed on Io, one of Jupiter's moons and the most geologically active body in the solar system.
"We saw a 300 percent change in the signal coming from this planet, which is the first time we've seen such a huge level of variability in an exoplanet," said lead author Brice-Olivier Demory of the University's Cavendish Laboratory, according to the press release. "While we can't be entirely sure, we think a likely explanation for this variability is large-scale surface activity, possibly volcanism, on the surface is spewing out massive volumes of gas and dust, which sometimes blanket the thermal emission from the planet so it is not seen from Earth."
55 Cancri e is a "super-Earth": a rocky exoplanet about twice the size and eight times the mass of Earth. It is one of five planets orbiting a sun-like star in the Cancer constellation, and resides so close to its parent star that a year lasts just 18 hours. The planet is also tidally locked, meaning that it doesn't rotate like the Earth does - instead there is a permanent "day" side and a "night" side.
Earlier observations of 55 Cancri e pointed to an abundance of carbon, suggesting that the planet was composed of diamond. However, these new results have muddied those earlier observations considerably and opened up new questions.
"When we first identified this planet, the measurements supported a carbon-rich model," said Madhusudhan, who along with Demory is a member of the Cambridge Exoplanet Research Center. "But now we're finding that those measurements are changing in time. The planet could still be carbon rich, but now we're not so sure - earlier studies of this planet have even suggested that it could be a water world. The present variability is something we've never seen anywhere else, so there's no robust conventional explanation. But that's the fun in science - clues can come from unexpected quarters. The present observations open a new chapter in our ability to study the conditions on rocky exoplanets using current and upcoming large telescopes."
Reference:
"Variability in the Super-Earth 55Cnc e," Brice-Olivier Demory, Michael Gillon and Nikku Madhusudhan, Monthly Notices of the Royal Astronomical Society [https://mnras.oxfordjournals.org], to appear online on May 5 (UK time).
