New Insights into Uranus: JWST Maps Atmosphere, Voyager 2 Data Re-analyzed

Recent scientific investigations have provided new insights into Uranus, utilizing both data from the James Webb Space Telescope (JWST) and a re-analysis of historical Voyager 2 observations. An international research team has mapped the vertical structure of Uranus's upper atmosphere, detailing temperature variations and auroral patterns. Separately, another study has proposed that a temporary space weather event may explain the unexpectedly intense radiation belt observed by Voyager 2 during its 1986 flyby.

JWST Unveils Uranus's Upper Atmosphere

An international team, led by Paola Tiranti of Northumbria University, has mapped the vertical structure of Uranus's upper atmosphere using the James Webb Space Telescope's Near-Infrared Spectrograph (NIRSpec). The observations, which covered nearly a full rotation of the planet, allowed researchers to study how temperature and charged particles vary with height in the ionosphere, up to 5000 kilometers above Uranus’s cloud tops.

Key findings from this research include:

• Temperature and Ion Density: Measurements indicated that temperatures peak between 3000 and 4000 kilometers, while ion densities reach maximum levels around 1000 kilometers. These showed longitudinal variations connected to the planet's magnetic field.
• Cooling Trend: Webb's data confirmed a continued cooling trend in Uranus's upper atmosphere, extending observations from the early 1990s. An average temperature of approximately 426 kelvins (about 150 degrees Celsius) was measured, which is lower than values previously recorded.
• Auroral Activity: Two bright auroral bands were detected near Uranus's magnetic poles. A distinct depletion in emission and ion density was observed in the region between these bands, a feature possibly related to transitions in magnetic field lines, similar to observations made at Jupiter.

Uranus's magnetosphere is characterized as one of the most unusual in the Solar System, being both tilted and offset from the planet’s rotation axis. This configuration results in complex aurora patterns across its surface, and the JWST observations illustrate how these effects penetrate deeply into the atmosphere.

JWST's observations provide unprecedented detail on how Uranus's unique magnetic field influences its complex auroral patterns and atmospheric structure.

The data is expected to enhance understanding of energy balance in ice giants and support the characterization of giant exoplanets. This study utilized data from JWST General Observer programme 5073 and was published in Geophysical Research Letters.

Re-evaluating Voyager 2: Uranus's Intense Radiation Belt

Scientists have proposed an explanation for the unexpectedly intense electron radiation belt around Uranus, which was observed by the Voyager 2 spacecraft in 1986. When Voyager 2 conducted its close-up flyby of Uranus, it measured a radiation belt significantly more intense than scientific predictions at the time. Voyager 2's 1986 mission also established Uranus as the coldest planet in the solar system.

New research, led by Robert Allen and Sarah Vines, space physicists at the Southwest Research Institute (SwRI), re-examined the historical Voyager 2 data. Their analysis indicates that a temporary space weather event may have intensified the planet's electron radiation belt during the flyby.

Radiation belts are formed by interactions between the solar wind and a planet's magnetic field, where energetic, charged particles from the sun's corona become trapped in the magnetosphere. The researchers compared the 1986 Voyager 2 observations with data collected from Earth orbit during a 2019 space weather event, finding similarities that suggest a similar phenomenon occurred at Uranus.

A temporary space weather event may explain the unexpectedly intense radiation belt observed by Voyager 2 during its 1986 flyby, challenging earlier predictions.

This study was also published in Geophysical Research Letters.