James Webb discovers best evidence for an exoplanet's atmosphere

Whether other planets are habitable or not is one of the fundamental questions that still has no answer. To date, more than 5000 exoplanets have been discovered, about which science knows very little. For example, until now there has been no reliable evidence of the existence of an atmosphere in rocky worlds like Earth. If the gas giant exoplanets show their atmosphere without hesitation, everything is very ambiguous in the case of rocky worlds. However, thanks to the James Webb space telescope, it became possible to discover the best evidence of the existence of an atmosphere on an Earth-like planet outside the solar system.

According to NASA, the capabilities of James Webb allow to collect data on the atmosphere of exoplanets. This is a rather narrow channel for receiving invaluable information, but it exists, and scientists are actively using it. If an exoplanet is hot enough or occurs between its star and Earth, James Webb records the emission and absorption spectra of the observed region and helps infer whether the planet has an atmosphere and what its approximate composition is.

In 2004, 41 light-years from Earth, in the binary system 55 Cancri near the sun-like star 55 Cancri A, scientists discovered the hot exoplanet 55 Cancri e, about twice the size of Earth and slightly denser. Since then, 55 Cancri e has been constantly under the attention of scientists, but the presence of an atmosphere on the exoplanet has not been confirmed in any way.

The exoplanet 55 Cancri e is too hot to support life. It orbits its star at a distance of about 17.5 million km (about a quarter of Mercury's distance from the Sun (70 million km). The surface of the planet appears to be a boiling ocean of magma. For scientists, this is a good opportunity to study the past of Earth, Venus or Mars, when the planets of our system were also quite hot. It is also an opportunity to understand the formation of atmospheres on rocky planets and their interaction with planetary material.

Observations of the exoplanet 55 Cancri e have revealed signs of a thick and thin atmospheric layer. According to the researchers, this is the best evidence of the existence of an atmosphere on rocky exoplanets in the entire history of observations of such objects. The data were obtained due to Webb's high sensitivity in the near and mid-infrared range.

Small variations in light, from 4 to 12 μm, revealed absorption of spectral lines that indicate the presence of carbon monoxide and carbon dioxide in the atmosphere of 55 Cancri e, apparently released and retained (most importantly in this study) by the global magma ocean. In other words, the rocky world independently creates and maintains an atmospheric layer. The primordial atmosphere would have long been destroyed by radiation from a nearby star.

James Webb also found that daytime temperatures on this exoplanet are cooler than modeled. Measurements have shown that the surface temperature during daytime is 1540 °C. If the planet had no atmosphere, the temperature would rise to 2000 °C or more. The cooling can be caused by either lava flows or the movement of atmospheric masses from the planet's dayside to its nightside (the planet appears to be in a constant tidal event, with one side always facing its star). According to scientists, the factor of lava flows can be ruled out, because it is clearly not the same dynamics. This is another indirect proof of the existence of an atmosphere in the exoplanet 55 Cancri e.

"Ultimately, we want to understand what conditions allow a rocky planet to sustain a gas-rich atmosphere, a key component of a habitable planet," the researchers wrote.