The star TRAPPIST-1 and the seven known planets that surround it are a natural laboratory in which the evolution of rocky planets can be studied. This has led many scientists to focus their attention on them, in search of a possible habitable planet. However, observations made by an international team of astronomers with the help of the James Webb Space Telescope They are not very encouraging.
Planets without atmosphere. The James Webb Space Telescope has a very powerful infrared radiation analysis instrument, with which it can analyze the temperature of the planets it observes. These emit infrared radiation whose intensity is proportional to their temperature, so a thermal map can be made. That’s what these astronomers have done.
They have initially focused on two of the planets that orbit TRAPPIST-1: TRAPPIST-1a and TRAPPIST-1b. The resulting heat map shows that neither planet has an atmosphere. They may have had it one day, but possibly TRAPPIST-1 itself destroyed it. It is a very uninspiring result for the search for habitable planets in this system.
Lights and shadows of TRAPPIST-1. So far seven exoplanets have been discovered orbiting TRAPPIST-1. They are all very close together. In fact, its seven orbits are concentrated in the distance between Mercury and the Sun. What happens is that this red dwarf is less energetic than our Sun, so the temperature would not be as suffocating. All of these planets are rocky, like Earth, and in fact, some are very similar in size. There could be an exoplanet with conditions similar to ours.
The problem is that red dwarfs They emit a lot of radiation and energetic flows of particles that could destroy their atmosphere.. And of course, without atmosphere, there is no life.
Tidal lock. All planets in the TRAPPIST-1 system are tidally locked. This means that its rotation and translation period around the red dwarf they are synchronized. As a result, there is one side continuously exposed to the star and another on the opposite side. On one side it is always day and on the other it is always night.
NASA/JPL-Caltech
Extreme temperatures. When a planet is tidally locked, there can be two situations, depending on whether it has an atmosphere or not. When there is an atmosphere, heat flows from the light side to the dark side, so that the entire planet has a stable average temperature.
On the other hand, if there is no atmosphere, the dark side can be frozen and the illuminated side can be scorched. In the two exoplanets analyzed by James Webb, it has been seen that temperatures are around 100ºC-200ºC on the illuminated side and -200ºC on the dark side. Therefore, it is confirmed that there is no atmosphere.
And now what? Despite this hard blow, there is still hope. The two exoplanets that have been analyzed are not in the star’s habitable zone. This is the distance from it at which the temperature is adequate for the water, if any, to remain in a liquid state.
At that exact point there are only TRAPPIST-1e, TRAPPIST-1f and TRAPPIST-1g. Furthermore, the former has a density and size very similar to those of Earth. James Webb has all his attention on this exoplanet right now, to repeat the process. If there were an atmosphere on it, it could still remain on the list of possible habitable planets.
It’s still interesting. Despite the first blow, TRAPPIST-1 remains a very interesting system for understand the evolution of rocky planets. The Earth was lucky not to lose its atmosphere; but, beyond those, the evolutions can be similar. Furthermore, we have not yet ruled out that TRAPPIST-1e has an atmosphere. Let’s go step by step.
Image | NASA, ESA, CSA, Joseph Olmsted (STScI)
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