Using data from the James Webb Space Telescope (JWST), astronomers have unraveled some of the atmospheric secrets of a strange, scorching hot world that has the consistency of a marshmallow. The extrasolar planet, or exoplanet, under JWST’s watchful infrared eye is WASP-17b, located about 1,300 light-years away. The exoplanet has a mass about 0.8 times that of Jupiter, but is about twice as wide as the largest planet in the solar system, giving it a “super puffy” consistency comparable to that of the terrestrial planet. WASP-17 b is so close to its parent star that it completes an orbit in less than four Earth days, and this proximity also causes the temperature of this “hot Jupiter” to skyrocket. Given the extreme conditions of this exoplanet, it is not surprising that its atmosphere is also quite unusual. Using a new technique called transmission chains, a team of scientists mapped the contours of WASP-17b’s atmosphere. They discovered that the atmosphere is shaped like a ring from which prominent “gems” emerge. “Planets are temperamental, their atmospheres are complex and chaotic,” team member Hannah Wakeford from the University of Bristol said in a statement. “The fact that all these numbers came together and showed us this very structured and dynamic picture of this giant world more than 1,000 light years away was really exciting.” Astronomers like WASP-17b so much that they put a ring on it. WASP-17b is so close to its parent star that it is tidally locked, meaning one side permanently faces the star; its dayside is constantly bombarded with stellar radiation. Conversely, the planet also has a cooler night side, which faces off into space in perpetuity. By creating incredibly complete 3D views of this exoplanet’s atmosphere, researchers discovered that WASP-17b’s atmosphere has a chemical composition and temperature that changes between the day and night sides based on theory and modeling. This was possible because the transmission chain technique tracked WASP-17b as it crossed or transited in front of its star, capturing the composition of light around the edge of the planet’s atmosphere, or limb, from different angles. This method outperforms standard approaches because traditional modeling only maps light as an average across the entire limb. “Instead of assuming that its atmosphere is a circle with the same radius on all sides, our technique allows you to calculate different distances from the center to the edge of the planet,” said Lili Alderson of Cornell University. “We can go around the edge.” So, we’ve moved from a ring to understanding where in the ring the gemstones are, so to speak. “That the morning and afternoon sides should have a strong temperature difference, and WASP-17b fits very well into that trend, pretty much what we thought it would be,” Alderson said. The successful application of the transmission chain method is an exciting step forward in modeling the atmospheres of the more than 6,000 worlds in NASA’s exoplanet catalog. star, what we predicted should be happening is happening,” Alderson concluded. “Going beyond the computational exercises and actually seeing it is a different matter.” The team’s research was published Wednesday (Oct. 14) in the journal Nature Astronomy.
