Researchers Discover Atmosphere Around Rocky Exoplanet 55 Cancri e, New Evidence Published in Nature Journal

After an atmosphere previously discovered around dozens of gas giants outside our solar system, there is now – finally – reasonably certain evidence that there is an atmosphere around a rocky exoplanet: 55 Cancri e.

This was announced by an international team of researchers, including scientists from the Leiden Observatory and SRON. Their findings will appear in the journal this week Nature.

Over 55 Cancri e
The research article revolves around 55 Cancri e. This planet is located about 41 light-years away from Earth and orbits – along with four other planets – around the sun-like star Cancri. 55 Cancri e is almost twice the size of Earth, but only slightly denser than our planet. This means that the planet can be counted among the super-terrestrials. These are planets that are larger than Earth, but smaller than Neptune and are likely similar to the rocky planets in our own solar system.

Close orbit
55 Cancri e is close to its parent star, which means it is very hot and most likely has a molten surface. It is best to think of that surface as a sea of ​​boiling magma. This close orbit may also ensure that the planet has both a day and a night side, with the day side always pointing towards the mother star and the night side always facing it. depart from the mother star.

Atmosphere?
55 Cancri ea was already discovered in 2011. And since then, researchers have also been wondering if this exoplanet could have sentience. That itself is not obvious and certainly not when we look at the conditions in which 55 Cancri e is found; these do not appear to be very immediately beneficial for maintaining an atmosphere. Because, as mentioned, 55 Cancri is very close to its parent star – about 25 times closer than Mercury is to the Sun. As a result, the planet not only has a very high temperature, but it is also constantly bombarded with radiation and solar wind from its parent star.

James Webb
But new measurements from the James Webb Telescope now strongly suggest that these conditions cannot prevent 55 Cancri e from having an atmosphere. Researchers drew that conclusion after using James Webb to measure infrared light between 4 and 12 microns coming from 55 Cancri e as the planet orbited its parent star. The researchers were particularly interested in the brightness while the planet was behind the parent star – in fact, they only measured the brightness of the parent star. They then also measured the brightness when the planet was next to the parent star – or the brightness of the parent star and the planet together. By subtracting the brightness measured when 55 Cancri e was behind the parent star from the brightness measured when 55 Cancri e was next to the parent star, the researchers could research to find out how much infrared light there was at different wavelengths coming from the side of the day. planet, calculation.

Heat energy
The researchers found the first indication that 55 Cancri e had an atmosphere when they studied a temperature measurement based on heat energy – which is given in the form of infrared light. These revealed that the daytime temperature was around 1540 degrees Celsius. That’s a high temperature, but not as high as the researchers would have expected if 55 Cancri e had no (significant) atmosphere. In that situation, according to the calculations, the day side would have to reach a temperature of 2200 degrees Celsius. The fact that the temperature is lower on the day side shows that there is an atmosphere where the energy from the day side (hot) is distributed to the night side (cooler). It may be an atmosphere full of volatile substances.

Carbon monoxide or carbon dioxide
Its existence is further supported by other measurements by Webb. “We see evidence of a decrease in the spectrum between 4 and 5 microns,” says researcher Aaron Bello-Arufe. “Less of this light reaches the telescope. This indicates that there is an atmosphere containing carbon monoxide or carbon dioxide, which absorbs this light.”

The Spitzer space telescope also previously studied 55 Cancri e and in particular the question of whether this exoplanet had an atmosphere. The observations indicated that there was an important atmosphere, made up of volatile substances. But the Spitzer data could be interpreted in another way as well. And in that other situation, 55 Cancri e was just ‘bare’, except for a thin layer of evaporated rock – rich in elements such as silicon, iron, aluminum and calcium. Given the situation in which 55 Cancri finds himself, that was certainly not an unthinkable situation; the planet is so hot that some of the molten rock on the surface is expected to evaporate. Webb’s new measurements are much clearer in that respect. The dip observed in the spectrum between 4 and 5 microns is not seen on a planet without an atmosphere or an atmosphere that contains only displaced rock. In other words, everything indicates that 55 Cancri e has a real atmosphere.

It is suspected that 55 Cancri he was not born with this atmosphere, but more or less created it himself. This is because gases – possibly carbon monoxide and carbon dioxide – are coming up from inside the planet. “Lava can store a lot of water and carbon dioxide,” says researcher Christiaan van Buchem. “So we think the lava ocean can act as a reservoir and supply gas to the atmosphere.”