Exoplanet TRAPPIST-1 b is comparable to Earth in size and mass, but is too close to its star. As a result, it has failed to maintain its atmosphere, without which its daytime side is permanently hotter than 200 degrees.
Located just 40 light years from us, the star TRAPPIST-1 is about ten times smaller than the Sun, but has an impressive system of seven planets. All are comparable to Earth in size, and three are within the "habitable zone," where it is warm enough for liquid water and maybe even life to exist.
The exact answer to the question of potential habitability depends on the presence and properties of the atmosphere, which can affect the temperature of the planet, for example through the greenhouse effect. But the high activity of a dwarf star can easily destroy any atmosphere, especially since all TRAPPIST-1 planets are closer to it than Mercury is to the Sun. On the other hand, the atmosphere on them can be constantly replenished by any geological processes. Therefore, the question of its presence in the planets near the red dwarfs is quite important.
The closest is the largest planet in the system, TRAPPIST-1 b. It makes a complete annual rotation in just one and a half of our days, receiving four times more radiation from its star than the Earth does from the Sun. The planet's radius is nearly equal to Earth's, but its mass is just under 0.8 Earth's, suggesting low density, possibly related to large amounts of water and/or other light substances.
However, new observations of TRAPPIST-1 b by the James Webb Space Telescope have shown that it has no atmosphere.
James Webb viewed TRAPPIST-1 b in the infrared during periods when the planet began and ended its passage behind its star. At such times, the telescope "sees" their total radiation. "Subtracting" the star's contribution, the radiation of the planet itself can be obtained by determining its temperature. For TRAPPIST-1 b it was about 230 degrees Celsius.
Because of the small size of the orbit, the planet is constantly turned to the star by the same side, as the Moon is turned to the Earth. Calculations predict that if TRAPPIST-1 b had an atmosphere, it could distribute heat more evenly. But new data have shown that the daytime side of the planet gets too hot, which means there is no atmosphere on it.
Apparently, no geological processes - even if they occur on TRAPPIST-1 b - have proven unable to make up for the constant erosion of light compounds associated with the influence of the close and restless red dwarf.
