Something supercharged Uranus with radiation during Voyager flyby 40 years ago. Scientists now know what.

Forty years ago, NASA's Voyager 2 spacecraft flew past Uranus and observed radiation levels that defied explanation. Now, scientists may finally know exactly what happened!

(An illustration of the solar storm that may have triggered the unusual magnetic activity spotted on Uranus during Voyager’s flyby. (Image credit: NASA/JPL-Caltech)

Something supercharged Uranus with radiation during Voyager flyby 40 years ago. Scientists now know what.

LIVE SCIENCE, Feb 11, 2026

Scientists may have solved a long-standing mystery surrounding Uranus' extraordinarily strong radiation belt.

A new analysis of Voyager 2 data suggests that a temporary space weather event may have made the planet's electron radiation belt more intense than usual as Voyager 2 was passing by. The findings could help to explain why the radiation belt was so much stronger than scientists had predicted it would be.

Radiation belts are formed from interactions between the solar wind and a planet's magnetic field. The sun emits a continuous stream of protons and electrons from its outer atmosphere, called the corona. For planets that have a global magnetic field, including Earth and Uranus, some of those energetic, charged particles get trapped in the magnetosphere.

In January 1986, Voyager 2 flew by Uranus and measured the strength of its radiation belts. While the ion radiation belt was a little weaker than expected, the electron radiation belt was much more intense than scientists had predicted — close to the maximum intensity Uranus could sustain. Since then, scientists have tried to figure out how and why this was the case.

"Science has come a long way since the Voyager 2 flyby," Robert Allen, a space physicist at the Southwest Research Institute (SwRI) and coauthor of the new research, said in a statement. "We decided to take a comparative approach looking at the Voyager 2 data and compare it to Earth observations we've made in the decades since."

(Images: Two versions of Uranus images taken by the Voyager 2 spacecraft in 1986. Scientists may finally know what triggered inexplicably high radiation signals that Voyager observed during its historic flyby. (Image credit: NASA/JPL))

Earth versus Uranus

In the study, published in November 2025 in the journal Geophysical Research Letters, Allen and colleagues revisited data collected by Voyager 2 during its flyby of Uranus. They found several similarities between the Voyager data and the data collected from Earth orbit during a space weather event in 2019.

Uranus' unusually intense radiation belt may have been caused by a "co-rotating interaction region," the team found. A co-rotating interaction region occurs when high-speed solar winds overtake slower solar wind streams. The phenomenon could have accelerated electrons and added energy to the radiation belt, the researchers said.

DISCOVERY: A day at Uranus just got 28 seconds longer

Did you know it takes 84 Earth-years for Uranus to orbit the sun once? On top of that amazing fact, astronomers have just discovered that 1 day on Uranus is actually a little longer than previously thought! They figured it out by observing auroras! Today's blog explains that discovery.

(Credit: This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble — one for the ring and one for the auroras.ESA/Hubble & NASA, L. Lamy / Observatoire de Paris)

BEFORE YOU READ THE STORY: Like Earth, Uranus experiences auroras, but due to its unique tilted magnetic field, they occur in unusual locations, including the equator and even the southern hemisphere, and are detected in infrared wavelengths.  

A day at Uranus just got 28 seconds longer 

By MARCIA DUNN, AP, April 7, 2025

CAPE CANAVERAL, Fla. (AP) — A day at Uranus just got a little longer.

Scientists reported Monday that observations by the Hubble Space Telescope have confirmed it takes Uranus 17 hours, 14 minutes and 52 seconds to complete a full rotation. That’s 28 seconds longer than estimates by NASA’s Voyager 2 spacecraft in the 1980s.

A French-led team studied a decade’s worth of aurora observations at the ice giant to track its magnetic poles. That long-term tracking provided a more precise rotation period for Uranus, the seventh planet from the sun. From that distance, it takes about 84 Earth years for Uranus to orbit the sun.

“The continuous observations from Hubble were crucial,” lead author Laurent Lamy of the Paris Observatory said in a statement.

Lamy and his international team said this new approach can help pinpoint the rotation of any world with auroras and a magnetosphere.

VIDEO:Auroras on Uranus Captured Again By Hubble | Video

The Hubble Space Telescope captured the first clear images of the auroras in 2011. In 2012 and 2014, the Space Telescope Imaging Spectrograph (STIS) aboard Hubble captured the phenomena again. -- Full Story: https://goo.gl/4qayFb  

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Published in the journal Nature Astronomy, the findings come a few weeks before the 35th anniversary of Hubble’s launch. NASA’s space shuttle Discovery delivered the space telescope to orbit on April 24, 1990. ___