For the first time, astronomers have created a detailed climate map of an Earth-sized planet orbiting another star. Using NASA's James Webb Space Telescope, an international team measured the temperatures of TRAPPIST-1b and TRAPPIST-1c, two rocky worlds in a distant star system. The results are surprising: neither planet appears to have a thick atmosphere.
On TRAPPIST-1b, the day side reaches about 217 degrees Celsius, hot enough to melt lead. Meanwhile, the night side is so cold that the telescope cannot detect any heat at all. This extreme temperature difference is the key discovery. If these planets had thick atmospheres, winds would carry heat from day to night, smoothing the temperatures. Instead, the difference between the two sides exceeds 400 to 500 degrees Celsius.
Both planets are tidally locked, meaning one side always faces their star while the other remains in permanent darkness. The research team, led by Michaël Gillon from the University of Liège, used Webb's infrared instrument to observe the planets for 60 hours of continuous observation.
The TRAPPIST-1 system lies about 40 light-years away in the constellation Aquarius and contains seven Earth-sized planets. At least three sit in the habitable zone. Scientists now hope to study the remaining planets to find worlds with atmospheres and better conditions for possible life.