Uranus isn’t as weird as scientists thought; it just took nearly 40 years to find out why
Voyager 2's flyby painted Uranus as an outlier of the solar system when the spacecraft showed the planet had a magnetic field nearly devoid of plasma. According to a new study, Voyager’s visit was just bad timing for Uranus.
Discovering Uranus
Uranus was discovered 241 years ago.
NASA’s Voyager 2 flyby in 1986 provided the only close-up look at Uranus. Nearly 40 years later, scientists are looking back at this data and finding out the visit happened during a strange space weather event.
Uranus is still an oddball, rotating sideways and taking 84 years to orbit the Sun. But Voyager’s flyby set up Uranus to be an outlier of the solar system when the spacecraft showed the planet had a magnetic field nearly devoid of plasma with nothing to feed the electron radiation belts.
According to a new study, Voyager’s visit was just bad timing for Uranus.
This zoomed-in image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam) Feb. 6, 2023, reveals stunning views of the planet’s rings. (SCIENCE: NASA, ESA, CSA, STScI / IMAGE PROCESSING: Joseph DePasquale (STScI) / NASA)
Scientists published their findings this week after taking another look at the 38-year-old flyby data and found that just a few days before the flyby, a dense slap of plasma from the Sun had reached out and "squashed" the planet’s magnetospheres in a rare space weather event.
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The suppressed magnetosphere was a surprise because the electron radiation belts were intense – second only to Jupiter in the solar system, according to NASA.
Study authors say this oddity was likely created by solar wind, a space weather event when plasma from the Sun drove plasma out of the Uranus system.
The first panel of this artist’s concept depicts how Uranus’s magnetosphere — its protective bubble — was behaving before the flyby of NASA’s Voyager 2. The second panel shows an unusual kind of solar weather was happening during the 1986 flyby, giving scientists a skewed view of the magnetosphere. (NASA/JPL-Caltech)
"Such a compression of the magnetosphere could increase energetic electron fluxes within the radiation belts and empty the magnetosphere of its plasma temporarily," the study authors wrote. "Therefore, the interpretation of Uranus’s magnetosphere as being extreme may simply be a product of a flyby that occurred under extreme upstream solar wind conditions."
If Voyager 2 had flown by Uranus days before or later, the planet's magnetosphere would have looked different. According to the study, these conditions likely only existed around the time of the flyby.
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Voyager 2 project scientist Linda Spilker said the new analysis "will change our view of Uranus once again."
A mission to Uranus is considered a high priority for space agencies in the decades to come. NASA has plans to explore a possible flagship mission, including an orbiter to Uranus and a probe dropped into the atmosphere in the next decade.