Discovery of the first rocky atmosphere of an exoplanet on Cancri 55 e

It is a historic discovery, if confirmed, of the first atmosphere of a rocky planet outside the solar system. This was one of the goals of the James Webb Telescope: to capture the spectrum of a small, rocky planet like Earth. It's done, it's called Cancri 55e, even if there's nothing hospitable about it because it's a very hot world.

Mathilde Fontes, editor-in-chief of the scientific journal epsilon, He tells us about this discovery published in the scientific journal nature: The first discovery of the atmosphere of a rocky planet outside the solar system.

franceinfo: Is Cancri 55e a planet like Earth, but outside our solar system?

Mathilde Fontes: Yes, it's a very, very distant planet. It is located 41 light-years from Earth. So it is impossible to go there. But we see it with telescopes. It is called Cancri 55 and was discovered in 2004.

In 2022 and 2023, it was targeted by the powerful James Webb Space Telescope. An analysis of these results has just been published. For the first time, we appear to have detected an atmosphere around a rocky exoplanet, like Earth.

When were exoplanets first discovered?

The first was discovered in 1995. There are more than 5000 of them. There are exoplanets everywhere, around almost every star. By studying their eclipses, and the way they filter light as they pass in front of their star, astrophysicists have already succeeded in analyzing the atmospheres of the largest of them, the gas giants. But even then, we could never see the rocky planet's atmosphere.

This has been one of the great goals of the James Webb Telescope from the beginning. Cancri 55e is one of these terrestrial planets. Even if it is very different from our Earth, because it is twice as large and, more importantly, orbits close to its star. Therefore, it is very hot, reaching a temperature of 2000 degrees according to thermal studies conducted by researchers. Its surface is likely to be a huge ocean of molten rock.

What's the atmosphere like?

The researchers concluded that there is a layer of gas that is a few percent of the planet's radius, which is somewhat similar to Earth (for us it is 7%). It will be an atmosphere of carbon, perhaps carbon dioxide, or carbon monoxide. All of this is conditional because the results have just been published as part of an accelerated scientific publishing process – and this is for the James Webb Telescope, which has generated a lot of scientific competition.

The expert community will now discuss and test this data. But the quest is moving forward. The ability to see and study other planets of the same type as our own, to finally see their diversity.