JWST has searched for and failed to locate a thick atmosphere on an exoplanet in one of the most intriguing planetary systems ever discovered for the second time.
The James Webb Space Telescope (JWST) has searched for and failed to locate a thick atmosphere on an exoplanet in one of the most intriguing planetary systems ever discovered for the second time. Just as they reported months ago for its neighbour TRAPPIST-1 b, astronomers report today that there is likely no alluring atmosphere on the planet TRAPPIST-1 c.
The possibility still exists that some of the TRAPPIST-1 system’s five other planets may have thick atmospheres containing geologically and biologically intriguing substances like carbon dioxide, methane, or oxygen. The two planets that have been studied thus far, however, appear to lack or have almost no atmosphere.
This type of planet is common around many stars, which “definitely reduces the number of planets which might be habitable,” says Sebastian Zieba, an exoplanet researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. He describes the discovery in Nature with his colleagues.
All seven of the TRAPPIST-1 planets, which are about the size of Earth and orbit a star about 12 parsecs (40 light years) away from us, have rocky surfaces. One of the best natural laboratories for studying how planets form, change, and possibly become habitable, according to astronomers, is the system.
JWST, which was launched in 2021 and is powerful enough to probe the atmospheres of the planets in greater detail than other observatories like the Hubble Space Telescope, is a key target for the planets.
An M dwarf, a faint, cool star in the Milky Way, serves as the planets’ host star. It releases ultraviolet radiation, which might harm nearby planets.
The innermost planet, TRAPPIST-1 b, lacks a significant atmosphere because it receives four times as much radiation from the Sun. However, TRAPPIST-1 c, which is further away from its star, might have been able to sustain a stronger atmosphere.
Zieba’s group used JWST to point at the TRAPPIST-1 system four times in October and November, which allowed the researchers to determine that TRAPPIST-1 c’s surface temperature on the side facing its star registers at about 107 °C. This temperature is too high to support a thick atmosphere rich in carbon dioxide.
The researchers also came to the conclusion that TRAPPIST-1 c would have formed with very little water, less than ten Earth oceans’ worth. This was done by comparing the observations with models of the planet’s potential chemistry.
TRAPPIST-1 c probably never had many conditions for habitability due to its low water content at its formation and the absence of a dense carbon dioxide atmosphere today.
The fourth and fifth TRAPPIST-1 planets, e and f, are the ones that are most distant from the star, but planetary scientist Joshua Krissansen-Totton hypothesises that they may still have substantial atmospheres. Unlike planets b and c, these planets are situated far enough from the star to prevent water from being blasted away.
The discoveries regarding planets b and c, however, might not offer much information regarding the atmospheres of the outer planets. Regarding the likelihood that the outer planets will retain atmospheres, Krissansen-Totton has remained ambivalent.