Hell On (Super-)Earth: Extreme Exoplanet Volcanism Spied

Using data from NASA’s Spitzer Space Telescope, astronomers have revealed wild atmospheric changes on a well-studied exoplanet — changes that they suspect are driven by extreme volcanic activity.

Over a period of two years, the team, led by University of Cambridge researchers, noted a three-fold change in temperature on the surface of 55 Cancri e. The super-Earth planet orbits a sun-like star 40 light-years away in the constellation of Cancer. It is twice the size of Earth and eight times our planet’s mass.

55 Cancri e is well-known to exoplanet hunters as the “diamond planet” — a world thought to be carbon-rich, possibly covered in hydrocarbons. But this new finding, published today in the arXiv pre-print service, has added a new dimension to the planet’s weird nature.

“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 co-author Nikku Madhusudhan, of Cambridge’s Institute of Astronomy, in a press release. “No signature of thermal emissions or surface activity has ever been detected for any other super-Earth to date.”

“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 Cambridge’s Cavendish Laboratory. “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.”

Spitzer measurements of the “day-side” of the exoplanet revealed a temperature swing of 1,000 to 2,700 degrees Celsius (1800-4900 degrees Fahrenheit), hinting that the surface of 55 Cancri e is molten and undergoing intense volcanic eruptions as it orbits its star, 55 Cancri. The exoplanet is the innermost world in the 55 Cancri system of five known exoplanets with an extremely compact orbit around the star. It completes one orbit every 18 hours and is tidally locked with its star (one hemisphere is in constant daylight, facing the star).

In our solar system, we know of one place that is wracked by volcanic activity as it completes its orbit around Jupiter. The moon Io is driven by intense tidal interactions with the solar system’s largest gas giant planet, causing intense volcanic activity that can be seen from Earth. The volcanism on 55 Cancri e, however, is many more times intense than Io’s.

This discovery, although preliminary, has thrown a wrench in the previous “diamond planet” model of 55 Cancri e.

Read more at Discovery News