Webb result reduces chances in the search for habitable planets – 06/25/2023 – Sidereal Messenger

Astronomers expected to detect a planet similar to Venus, with a dense atmosphere, but what the James Webb Space Telescope revealed was a colder and airless world, a finding that reduces the chances of finding habitable worlds around red dwarf stars – smaller, cooler, and more common stars than the Sun.

The news comes from the Trappist-1 system, home to seven planets comparable in size to Earth, with three of them in the so-called habitable zone, where a world located there with an atmosphere similar to Earth’s would be able to preserve liquid water on the surface. .

In March, researchers led by Thomas Greene of NASA’s Ames Research Center announced Webb results for the innermost of these, Trappist-1 b. Infrared detection from the planet indicated a temperature of over 230 degrees Celsius on the dayside and the absence of an atmosphere.

Now, Sebastian Zieba of the Max Planck Institute for Astronomy in Germany and his colleagues report in the journal Nature similar observations concerning the system’s second planet, Trappist-1 c.

Again, the thermal emission from the dayside of the planet was measured, comparing the infrared brightness when it passed behind its parent star (the so-called secondary eclipse) and immediately before and after that. By subtracting one observation from the other, it is possible to keep only the radiation coming from it and estimate its temperature – in this case, just over 100 degrees Celsius.

That in itself is a record: never has a rocky exoplanet so cold, just slightly above the boiling point of water at sea level on Earth, had its temperature directly measured by this method.

On the other hand, astronomers hoped to detect a higher temperature, boosted by a dense atmosphere like that of Venus, with its equivalent greenhouse effect. However, observations once again ruled out an appreciable gaseous envelope. If Trappist-1 c has an atmosphere, it will be very rarefied.

Not at all unexpected, but still frustrating. Red dwarf stars are known to start their lives extremely active, and their stellar explosions can sweep away the atmosphere of surrounding worlds. But astronomers hope that, in some cases, it is possible for them to retain, or at least regain, a layer of air after the star calms down – an essential factor for the habitability of a planet (no air, no liquid water on the surface, even at mild temperatures).

As Abel Méndez, of the University of Puerto Rico’s Planetary Habitability Laboratory joked, “two planets are gone, five still to be checked”, of Trappist-1’s seven. If they are all worlds without an atmosphere, this reinforces the idea that red dwarfs would not even be suitable targets for the search for habitable planets – which would lead us to throw away three-quarters of the galaxy’s systems. And the worst: precisely those that we can study more easily through our current telescopes.

This column is published on Mondays in the printed version, in Folha Corrida.

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