New study finds evidence of an atmosphere on a rocky planet for the first time

Just 41 light years from Earth is an exoplanet so incredibly hot scientists didn’t think it could maintain an atmosphere, but a recent study published in Nature by a national team of scientists suggests 55 Cancri e may be the first rocky exoplanet confirmed to have an atmosphere.

Researchers from NASA’s Jet Propulsion Laboratory, the California Institute of Technology, the University of Chicago, the University of New Mexico, and others published their findings in a paper titled “A Secondary Atmosphere on the Rocky Exoplanet 55 Cnc e.”

The exoplanet 55 Cancri e, orbits a star similar to Earth’s sun, but unlike Earth, it orbits its star from an exceptionally close distance making the planet molten hot and uninhabitable. While it takes Earth about 365 days to orbit the sun, the exoplanet completes its full orbit in less than one Earth day, according to NASA. It’s so close to its star that gravity doesn’t allow it to rotate, so for billions of years one side has experienced day and the other night. The extreme environment of this planet should mean that it would be unable to maintain the primordial atmosphere it was born with when it formed.

In this study, scientists hypothesize that instead, seas of magma continually replenish and maintain a secondary atmosphere. This secondary atmosphere likely formed later in the planet’s existence, in this case generated from the intense volcanic activity triggered by the proximity to the star.  

UNM Physics and Astronomy Assistant Professor Diana Dragomir was part of the recent study, though she was already well-acquainted with the exoplanet after contributing to the discovery of its transits in her doctoral thesis. Exoplanet 55 Cancri e’s density and heat have long led to complex questions for her and others who study exoplanets.

“Ever since its discovery, this planet has defied multiple attempts at understanding its properties and composition. This discovery is the clearest piece of information we have obtained so far for 55 Cancri e,” Dragomir said.  

The discovery would not be possible without the James Webb Space Telescope, which allows researchers to study exoplanets with greater precision than ever before. The team used images from the Webb telescope to analyze light emitted by the exoplanet and its star. To do that, they first had to translate the images into light spectra. They then compared the observations to spectra created from different combinations of elements and molecules to hypothesize what potential atmospheric compositions the exoplanet might have. This study is among the first to use data from the Webb telescope for this kind of investigation and the models used in the study could provide future researchers with a process to complete similar work for other exoplanets.

The research team hypothesizes that the exoplanet’s atmosphere could be composed of vaporized rock rich in carbon, carbon monoxide and carbon dioxide. While further research is needed to confirm the results, the exoplanet’s light emissions and models of carbon-rich atmospheres seem to align closely. While researchers know 55 Cancri e’s extremely harsh conditions make it uninhabitable, the discovery of its atmosphere confirms that the newest telescopes available to scientists may finally be sensitive enough to study distant rocky planets in detail. Michael Bess, who graduated last Spring with a degree in Astrophysics worked with Dragomir on UNM’s portion of the project translating the images into spectra and running models to help narrow down potential atmosphere compositions. 

“Studying the atmospheres of exoplanets can tell us a lot about planets in different stages of formation,” Bess said. “Eventually, we may be able to look at similar planets for habitability because a planet with an atmosphere similar to ours could possibly have life.”

When Bess approached Dragomir about getting involved with her research, he never expected to work on such a large-scale project.

“It was really exciting,” Bess said about working on such a significant project as an undergraduate. “I thought it was so fascinating and new and interesting to be able to work with this brand new amazing telescope and amazing people from NASA. It was a lot of fun and a lot of work and I enjoyed every second of it.”

Several teams, including Bess and Dragomir, each analyzed the data individually and then met to compare results. It was found that the results obtained by all the teams agreed, which supported that the interpretation of the data was correct. It was an exciting moment not only for the entire research team but especially for Bess whose skill level working on the project became on par with that of researchers who had already completed Ph.Ds.

“You’ve got an undergrad student who analyzed the data sets at a level comparable to what his much more senior collaborators did,  and he was also able to communicate and coordinate with the entire team independently ” Dragomir said. “I'm really proud of Michael for that.”

Bess will begin his Ph.D. in Astrophysics this Fall at the University of Florida. If he chooses to continue research on 55 Cancri e, there will still be much to discover.

Without an atmosphere to help retain heat, it’s likely the side of 55 Cancri e in eternal night would be around negative 400 degrees Fahrenheit.

“The presence of an atmosphere on 55 Cancri e also explains the warmer-than-expected temperature measured on the planet’s nightside. Even though that side never faces the star, the atmosphere helps circulate heat from the dayside all around the planet,” Dragomir said.

This work therefore also confirms previous claims that 55 Cancri e is a lava planet with a likely molten surface. Together with the new knowledge of its atmosphere, scientists can begin to hypothesize about the composition of the rest of the planet. 

Further study is necessary to continue unlocking 55 Cancri e’s secrets, but until then, the most recent discovery is out-of-this-world.