Scientists have spotted a rocky exoplanet with a possible atmosphere that they believe may have sprung from a magma ocean on a distant world.
The planet is called 55 Cancri e. It is about 41 light-years from Earth and, according to the team’s observations, has a layer of gases above its surface that may represent an atmosphere. 55 Cancri e is a super-Earth, a rocky body roughly 8.8 times the size of our world with an equilibrium temperature of about 2,000 Kelvin, or 3,140 degrees Fahrenheit. The team’s findings were published today in nature.
“55 Cancri e is one of the most enigmatic exoplanets,” Bryce-Olivier Demory, an astrophysicist at the University of Bern and co-author of the study, said in a university news release. “Despite the vast amount of observation time obtained with a dozen ground-based and space-based instruments over the past decade, its very nature remained elusive until today, when pieces of the puzzle can finally be assembled thanks to the James Webb Space Telescope (JWST ).”
Webb conducts science operations from a point about one million miles from Earth nearly two years, providing many insights into the formation of galaxies, ancient light sources, distant exoplanets, and even the other worlds in our own solar system. The team studied the exoplanet using the Webb Near Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI), the two main imagers. “The measurements rule out the scenario where the planet is a lava world enveloped by a thin atmosphere composed of vaporized rock,” the researchers wrote in their study, “and indicate a bona fide volatile atmosphere, possibly rich in [carbon dioxide] or [carbon monoxide].”
The planet is tidally locked, meaning that one of its sides faces its host star at all times (just as the near side of the Moon always faces Earth). But measurements of the daytime temperature of 55 Cancri turned out to be colder than the team expected — evidence that the atmosphere is spreading heat around the planet.
“There are many observations of exoplanet atmospheres, but they all have massive hydrogen-dominated atmospheres,” said Renyu Hu, a planetary scientist at NASA’s Jet Propulsion Laboratory and lead author of the study, in an email to Gizmodo. “Here we finally got an observation of an atmosphere around a rocky exoplanet.”
Although 55 Cancri e is inhospitable to life as we know it, it is a useful case study for showing how the Webb Telescope can characterize distant worlds without imaging them directly. Rocky exoplanets, unlike giant gas giants, are very difficult to image directly; they are not as bright as stars and are much less massive. Instead, scientists recognize aspects of the exoplanet’s structure using the stars they orbit. A recent research team identified the possible atmosphere of 55 Cancri e by carefully measuring the amount of light that comes from the planet as it orbits its star. The Next-Generation Habitable Worlds Observatoryif it leaves Earth, it will make it much easier to recognize aspects of distant exoplanets, potentially increasing scientists’ ability to detect life beyond Earth.
Astronomers have documented more than 5000 exoplanets to date. These worlds must be scrutinized in order for researchers to separate the wheat from the chaff in terms of astrobiology; even looking at hostile worlds can shed light on how planets evolve and what kind of planetary diversity exists in space.
In March 2023, a different team of researchers found that rocky planet TRAPPIST-1b has no atmosphere, perhaps because its close proximity to its host star inhibits anything the planet can develop. The TRAPPIST-1 system is fascinating to astrobiologists because several of its worlds lie in the so-called “habitable zone,” making the worlds neither too hot nor too cold for life as we know it.
Atmospheres are critical to sustaining life, so as interest in the TRAPPIST-1 system wanes, 55 Cancri e emerges as a fascinating candidate for astrobiological research.
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