Spitzer telescope finds hot super-Earth 55 Cancri e likely has an atmosphere

Presence of an atmosphere best explains temperatures on the planet.
By Laurel Kornfeld | Nov 20, 2017
55 Cancri e, a hot super-Earth in a very close orbit around its parent star, likely has an atmosphere, according to a study of data collected on the planet with NASA's Spitzer Space Telescope.

Estimated to be about 8.63 Earth masses with about twice Earth's diameter, the planet is so close to the star that it is tidally locked to it, meaning one side always faces the star while the other always faces away from the star.

Because the planet's density is similar to that of Earth, scientists believe it is a rocky world rather than a gaseous one.

Spitzer's observations were conducted between June 15 and July 15, 2013, with a camera designed to observe in the infrared. A group of scientists who in 2016 studied the data Spitzer collected during these observations suggested the planet's extreme heat is caused by lava that flows in lakes on the star-facing side and hardens on the other side.

The researchers proposed surface lava on the day side reflects radiation from the star, in the process warming the entire planet.

However, a second study of the Spitzer data conducted this year determined the planet has an atmosphere composed of volatile materials similar to those in the Earth's atmosphere, meaning it could be extremely hot without any flowing lava on its surface.

Scientists conducting this study compared changes in the planet's brightness with computer models of energy flow and determined an atmosphere is the best explanation for surface temperatures.

Without an atmosphere, lava lakes on the surface would be exposed to space and heat only local regions rather than the whole planet.

"If there is lava on this planet, it would need to cover the entire surface. But the lava would be hidden from our view by the thick atmosphere," noted NASA Jet Propulsion Laboratory (JPL) astronomer Renyu Hu.

Among the latest research group's findings is the fact that the planet's night side is not as cool as initially thought. A large discrepancy between the temperatures of a planet's day and night sides is a characteristic of worlds that do not have atmospheres.

The researchers determined temperatures on the day side of 55 Cancri e average 4,200 degrees Fahrenheit (2,300 degrees Celsius). On the night side, temperatures range from 2,400 to 2,600 degrees Fahrenheit (1,300 to 1,400 degrees Celsius).

"Scientists have been debating whether this planet has an atmosphere like Earth and Venus, or just a rocky core and no atmosphere, like Mercury. The case for an atmosphere is now stronger than ever," Hu emphasized.

Even though it likely has an atmosphere, 55 Cancri e is not habitable for life as we know it because it is too hot to sustain liquid water.

A paper on the most recent study has been published in the Astronomical Journal.



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