For 80 hours, NASA’s Spitzer Space Telescope kept close tabs on 55 Cancri e. Because the planet orbits extremely close to its star (it completes one orbit every 18 hours), scientists could gather temperature data across the entire surface.

“Spitzer observed the phases of 55 Cancri e, similar to the phases of the moon as seen from the Earth. We were able to observe the first, last quarters, new and full phases of this small exoplanet,” said Brice Olivier Demory, lead author of the new report. “In return, these observations helped us build a map of the planet. This map informs us which regions are hot on the planet.”

55 Cancri e Spitzer observations

Did you know: 55 Cancri e has another name. Janssen. It’s named after Zacharias Janssen, who is associated with the invention of the first optical telescope. All of the Cancri planets are named after pioneers in the field of astronomy. The star 55 Cancri e orbits is also known as Copernicus.

The verdict? 55 Cancri e is hot, very hot. The exoplanet is tidally locked to its star, so that means one side is always facing the star. But that doesn’t mean the night side is cool. Scientists were surprised to see how much these temperatures varied, though. On the day side, temperatures hit a scorching 4,400 degrees Fahrenheit. The night side was cooler, but still hot at 2,060 degrees Fahrenheit.

What do the big differences in temperatures mean? 55 Cancri e is not distributing its heat very well. Scientists originally believed a thick atmosphere and winds were moving heat around the planet. If that were the case, we wouldn’t see such large temperature variations.

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So, what’s going on? One theory is the day side of the planet is covered in rivers and large pools of lava. As for the night side? “We think the night side would have solidified lava flows like those found in Hawaii,” said Michael Gillon, from the University of Liège, Belgium.

Data from the Spitzer telescope supports the idea of lava. The hottest area on 55 Cancri e isn’t directly under the blazing star. It’s shifted to one side. Either there is heat recirculation (atmosphere) exclusive to the day side, or lava flows are responsible.

Spitzer and ‘the sweet spot’

NASA’s Spitzer Space Telescope was never meant to take these kind of high-precision observations. But scientists and engineers will always find a way to get every sliver of performance out of the current hardware.

In Spitzer’s case, they found new ways to enhance Spitzer’s ability to measure brightness changes in exoplanet systems. One involved measuring “the sweet spot” – a single pixel on Spitzer’s detector.

“By understanding the characteristics of the instrument — and using novel calibration techniques of a small region of a single pixel — we are attempting to eke out every bit of science possible from a detector that was not designed for this type of high-precision observation,” said Jessica Krick of NASA’s Spitzer Space Science Center.

55 Cancri e still has many secrets for scientists to uncover. And the next generation of telescopes including the James Webb Space Telescope will be tasked with revealing them.

Image credits: NASA. Top image is an artist concept.

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