Using observations from the NASA/ESA/CSA James Webb Space Telescope, astronomers have detected the trihydrogen cation at Neptune as well as distinct infrared southern aurorae.
Emissions from the upper-atmospheric trihydrogen cation (H3+) have been used to study the global-scale interactions of Jupiter, Saturn and Uranus with their surrounding space environments for over 30 years, revealing the processes shaping the aurorae. However, despite repeated attempts, and contrary to models that predict it should be present, this ion has proven elusive at Neptune. Now, using observations from the NASA/ESA/CSA James Webb Space Telescope, astronomers have detected the trihydrogen cation at Neptune as well as distinct infrared southern aurorae. "In the past, astronomers have seen tantalizing hints of auroral activity on Neptune," said Northumbria University astronomer Henrik Melin and his colleagues. "However, imaging and confirming aurorae on Neptune have long evaded astronomers despite successful detections on Jupiter, Saturn, and Uranus." "Neptune was the missing piece of the puzzle when it came to detecting aurorae on the giant planets of our Solar System." In the study, the authors analyzed the data obtained by Webb's Near-Infrared Spectrograph (NIRSpec) in June 2023. In addition to the image of the planet,…