In 2004, thanks to studies of the radial velocity of the star Copernicus, similar to the Sun and located in the Cancer constellation, 55 Cancri e. was discovered. This rocky planet, 41 light years from Earth, has been the subject of intense research that, with the arrival of James Webb Space Telescope (JWST)have taken an unexpected turn.
A team of scientists led by Renyu Hu of JPL POTpublished a study in Nature where evidence of a possible secondary atmosphere in 55 Cancri e.
“This is the best evidence to date of an atmosphere on a rocky planet outside our solar system,” they say from the University of Bern.
Why is it called “super-Earth”?
55 Cancri e receives this name because of its size, larger than that of the Earth but similar to that of Neptuneand its composition similar to those rocky planets of our solar system. Its mass is 8.08 times that of Earth and it orbits a star similar to the Sun in size and brightness. However, their temperature differs radically.
The proximity to Copernicus (much greater than that of Mercury to the Sun) causes it to complete an orbit in just 18 hours, making it an extremely hot planet. It is possible that its entire surface is a magma ocean, not solid rock.
Its proximity to the star has also allowed scientists to determine that it does not rotate on itself, but rather that one of its sides is in permanent darkness while the other receives constant light. These characteristics, although they do similar to earth in some respects, they make it uninhabitable.
How was the possible atmosphere detected?
The JWST data were key to detecting the possible atmosphere. The University of Bern explains the process: “The team used JWST’s NIRCam (near infrared) and MIRI (mid infrared) cameras to measure infrared light coming from the planet.”
They compared the brightness according to the position of 55 Cancri e with respect to Copernicus, subtracting the total starlight when the planet was behind the star to that obtained when it was next to it. This allowed “the amount of infrared light from the planet’s dayside at multiple wavelengths simultaneously” to be measured, which in turn allowed scientists to theorize about its temperature.
The planet’s daytime surface was initially assumed to be around 2,200°C, but the results showed that it is significantly colder (around 1,500°C).
“This is a strong indication that the energy is distributed from the day side to the night side, probably due to an atmosphere rich in volatiles,” says Hu.
The supposed atmosphere would absorb part of the infrared radiation from the magma ocean, preventing the JWST from capturing it, hence its apparent lower temperature.
The term “secondary atmosphere” refers to an atmosphere that was not formed by the accumulation of layers during the formation of the planet (primary atmosphere), but is a product of volcanic activity.
In the case of 55 Cancri e, the proximity to its star would have destroyed any primary atmosphere due to the high temperatures and radiation. It is believed that the gases present in the overlying magma ocean “continuously replenish” the secondary atmosphere. The study rules out the possibility that the planet is a lava world with a tenuous atmosphere of vaporized rock, and points to a “bona fide volatile atmosphere, probably rich in CO2 or CO.”
These results demonstrate the great capacity of the JWST to detect and process information about extrasolar planets, hoping to find a habitable one in the future. Furthermore, never before has such promising evidence of an atmosphere been detected on a planet outside the solar system, much less on “a hot, highly irradiated rocky planet,” as the University of Bern claims.
Yes ok 55 Cancri e is not considered habitablestudying their atmospheric composition could expand knowledge about the functioning of rocky planets and how they manage to maintain an atmosphere rich in gases, necessary for the development of life as we know it.
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