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An international team of astronomers observed a rare stellar occultation event, where Uranus passed directly in front of a distant star about 400 light years from Earth.
This celestial alignment, visible only from Western North America, provided a unique opportunity to study the atmosphere and rings of the ice giant in unprecedented detail.
During the occultation, Uranus' atmosphere refracted and gradually dimmed the starlight before completely blocking it, then reversed the process as the star reappeared.
This produced a "light curve" that scientists analysed to measure temperature, density, and pressure at multiple altitudes within Uranus' stratosphere, the planet's middle atmospheric layer.
These measurements mark the first large-scale collaborative occultation campaign for Uranus, involving over 30 astronomers and 18 professional observatories coordinated by NASA's Langley Research Center.
The data collected will help researchers understand how Uranus' atmosphere functions and how it has evolved over the past 30 years since the last significant occultation in 1996.
One key mystery is the cause of the planet's upper atmospheric layers being inexplicably hot. Additionally, the observations will refine knowledge of Uranus' rings—composed of ice and dust—and its precise orbit around the Sun, which is currently only known to within about 100 miles.
Uranus, nearly 2 billion miles from Earth, is classified as an ice giant due to its interior of water, ammonia, and methane fluids with low freezing points.
Unlike gas giants with solid surfaces, Uranus' atmosphere offers a natural laboratory to study cloud formation, storms, and wind patterns without surface interference.
This stellar occultation builds on a successful test run in November 2024, when telescopes in Asia observed a dimmer Uranus occultation to calibrate instruments and improve timing predictions for the April event.
Future occultations over the next six years, including a brighter star event expected in 2031, will further enhance NASA's preparation for eventual missions to explore Uranus more closely, possibly deploying atmospheric probes.
