Signs of atmosphere around terrestrial planet

Published 15 May 2024 at 13.51

Domestic. The exoplanet 55 Cancri e probably has an atmosphere dominated by carbon dioxide or carbon monoxide, according to a new study published in Nature.

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40 light-years away from our own solar system lies the exoplanet 55 Cancri e. It orbits 65 times closer to its star than the Earth orbits the sun, resulting in a year lasting only 17 hours.

With its proximity to the star, the daily temperature becomes high enough that the surface melts and probably forms a giant ocean of lava.

The atmosphere around planets orbiting close to their star is strongly affected by stellar wind, a flow of gas from a star's upper atmosphere. Therefore, it has been speculated that the atmosphere around 55 Cancri e may have completely eroded away, leaving the planet atmosphereless. But now new observations with the James Webb telescope show that the planet likely has an atmosphere dominated by carbon dioxide or carbon monoxide.

– The existence of an atmosphere shows that it must be actively re-forming, perhaps through active volcanism driven by the planet's proximity to the star. Without regeneration, models show that the atmosphere would not survive very long, says Alexis Brandeker, senior lecturer at the Department of Astronomy at Stockholm University and co-author of the study.

Studying the atmosphere of 55 Cancri e is challenging even for The James Webb Telescope. The planet cannot be seen directly, but with the help of the telescope the researchers have examined the infrared light coming from the part of the planet that faces its star. They did this by observing an event called an occultation, which occurs when the planet passes behind the star. By comparing the difference in light between when the planet is behind the star and when it is right next to it, it is possible to calculate how much of the light comes from the planet.