Webb measures temperature on the rocky planet of Trappist-1 – 03/27/2023 – Sidereal Messenger

The James Webb Space Telescope was able to measure the daytime temperature of the innermost of the planets in the fascinating Trappist-1 system, which has seven planets comparable in size to Earth.

It is the first time such a measurement has been made for a rocky world outside the Solar System. The results suggest that the illuminated side of the planet Trappist-1 b has a temperature of around 500 Kelvin, equivalent to 230 degrees Celsius.

The observation also found no evidence of an atmosphere for that world, which is not entirely unexpected — previous measurements made with the Hubble and Spitzer Space Telescopes, less capable than Webb, had also found no signs of an air envelope.

The Trappist-1 system is of immense interest to astronomers because of the ease with which it is offered precisely for these studies of characterization of the planets. It is a red dwarf star, with less than 10% of the Sun’s mass, located 40 light years from here, in the constellation of Aquarius. It is a star with a low level of activity and advanced age (estimated at 7.6 billion years, with a large margin of error, plus or minus 2.2 billion).

The seven planets, discovered between 2016 and 2017, have diameters between 77% and 129% of Earth’s, which indicates that possibly all of them are rocky, three of which (planets d, e and e) in the so-called habitable zone – the band around the star where the level of radiation is compatible with the existence of liquid water on the surface.

All were identified by the transit method, which means that they periodically pass in front of the star with respect to Earth. That’s how Webb was able to detect the infrared light emission from Trappist-1 b. Impossible to detect their light individually, but it is feasible to detect a secondary eclipse, when the planet passes behind the star – allowing the telescope to detect only the starlight. Comparing it to the observation of when he is beside her, helping to compose the total light, it is possible to subtract one from the other and be left with what is emitted from the planet.

It is from this result that the group led by Thomas Greene, from the NASA Ames Research Center in California, was able to calculate that the planet is almost certainly devoid of atmosphere and has a temperature of 230 degrees Celsius on the dayside. The observations were published in the British scientific journal Nature.

Like the Moon around Earth, Trappist-1 b must be gravitationally locked, so that the same face of the planet is always facing its star. Without an atmosphere to distribute heat from the dayside to the nightside, the nighttime region must reach temperatures considerably lower than 0 degrees Celsius.

There is great anxiety for Webb results linked to the other planets in the Trappist-1 system. At 40 light years from Earth, it promises to be one of the first to be characterized in greater detail, going beyond the basic parameters of mass and diameter. Perhaps one of them, in the habitable zone, retains an atmosphere and the ability to conserve liquid water on the surface, in an environment favorable to life? Only the future will tell – but not long now.

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