New data from the James Webb Space Telescope reveals that Earth’s “sibling planet,” Trappist-1b, has daytime temperatures around 230°C.
Simulation of the rocky planet Trappist-1b orbiting the red dwarf star Trappist-1. (Image: NASA)
When the Trappist-1 system was discovered in 2017, astronomers were thrilled by the prospect that some of its seven rocky planets—similar in size and mass to Earth—might be habitable.
Located approximately 40 light-years away, these exoplanets orbit the red dwarf star Trappist-1 at much closer distances than the rocky planets in our Solar System. However, their star is “cooler” and emits significantly less energy than our Sun.
The Trappist-1 system has become a prime target for the James Webb Space Telescope, NASA’s most powerful space observatory, which has made a series of astounding discoveries since its first observations were released last July.
In a recent discovery published in the journal Nature on March 27, astronomers focused on Trappist-1b, the closest and most detectable planet in the Trappist-1 system. The Mid-Infrared Instrument (MIRI) on Webb measured the change in brightness as the planet passed behind the star in a phenomenon known as secondary eclipse.
Simulation of the Trappist-1 system, with Trappist-1b as the closest planet to the host star. (Image: AFP)
“Just before disappearing behind the star, the planet emits the most light because it almost solely shows its ‘daytime’ side,” said astrophysicist Elsa Ducrot from the French Atomic Energy and Alternative Energies Commission, co-author of the study, in an interview with AFP.
By subtracting the brightness of the star, researchers calculated the amount of infrared light emitted by this planet. Thus, the MIRI instrument can function like “a giant non-contact thermometer.”
According to NASA, the daytime temperature of Trappist-1b is about 230°C, “almost perfect for baking pizza.” However, the heat is not evenly distributed across its surface, a role typically played by an atmosphere.
Therefore, scientists concluded that Earth’s “sibling planet” has very little or no atmosphere. If it does have an atmosphere, it certainly lacks carbon dioxide, as the research team found no signs of light absorption by carbon dioxide.
Ducrot noted that previous space telescopes like Spitzer could not determine whether Trappist-1b had an atmosphere, despite observing 28 secondary eclipses. Webb’s capability to analyze atmospheric conditions will usher in a new era in the study of rocky exoplanets beyond our Solar System.
