James Webb telescope measures the temperature of Earth-like planets
New data from the James Webb telescope shows that Earth's "sister planet" has a daytime temperature of about 230°C.
Simulation of the rocky planet Trappist-1b orbiting the red dwarf star Trappist-1. Photo: NASA
When the Trappist-1 system was discovered in 2017, astronomers were excited at the prospect that some of its seven rocky planets - roughly the same size and mass as Earth - could have. habitable.
Only about 40 light-years away, these exoplanets orbit the red dwarf star Trappist-1 with orbits much closer than the rocky planets in the solar system. However, their star is "cooler" and radiates much less energy than the Sun.
The Trappist-1 system has created a clear target for James Webb, NASA's most powerful space telescope with a series of startling discoveries since the publication of its first observations last July. .
In the new discovery, published in the journal Nature on March 27, astronomers focused on Trappist-1b, the planet closest to its host star and easiest to detect in the Trappist-1 system. Webb's Mid-Range Infrared (MIRI) instrument measured the change in brightness as the planet moved behind the star, in a phenomenon known as a secondary eclipse.
Simulation of the Trappist-1 system, where Trappist-1b is the planet closest to the host star. Photo: AFP
"Just before disappearing behind the star, the planet emits the most light because it shows almost exclusively its 'daytime' side," said astrophysicist Elsa Ducrot from the Atomic Energy Commission and French Alternative Energy, study co-author, told AFP .
By subtracting the star's luminosity, the researchers calculated how much infrared light the planet emits. As a result, the MIRI device can act like "a giant touchless thermometer".
According to NASA, Trappist-1b's daytime temperatures are around 230°C, "almost perfect for baking pizza". However, the heat is not distributed throughout the surface, a role typically provided by the atmosphere.
Therefore, the scientists concluded that the "sister planet" of Earth "has little or no atmosphere". If it does, its atmosphere is definitely free of carbon dioxide because the team didn't see any sign of light being absorbed by carbon dioxide.
Ducrot said previous space telescopes like Spitzer could not tell if Trappist-1b had an atmosphere, despite observing 28 secondary eclipses. Webb's ability to analyze the atmosphere will open a new era in the study of rocky planets outside the solar system.