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- When Voyager 2 flew past Uranus in 1986<\/strong>, it found that the planet\u2019s magnetosphere wasn\u2019t what scientists expected.<\/li>\n
- The magnetosphere showed intense electron radiation belts<\/strong> but no source of energized particles to feed those active belts.<\/li>\n
- Now scientists found that the solar wind was the culprit<\/strong>, with a rare event that temporarily changed the magnetosphere while Voyager 2 was making its observations.<\/li>\n<\/ul>\n
NASA published this original story on November 11, 2024. Edits by EarthSky.<\/p>\n
Mysteries at Uranus<\/h3>\n
When NASA\u2019s Voyager 2 spacecraft flew by Uranus in 1986, it provided scientists\u2019 first \u2014 and, so far, only \u2014 close glimpse of this strange, sideways-rotating outer planet. Alongside the discovery of new moons and rings, baffling new mysteries confronted scientists. The energized particles around the planet defied their understanding of how magnetic fields work to trap particle radiation. And so Uranus earned a reputation as an outlier in our solar system.<\/p>\n
Now, new research analyzing the data collected during that flyby 38 years ago has found the source of that particular mystery is a cosmic coincidence: It turns out that in the days just before Voyager 2\u2019s flyby, the planet had been affected by an unusual kind of space weather. This space weather event squashed the planet\u2019s magnetic field, dramatically compressing Uranus\u2019 magnetosphere.<\/p>\n
Jamie Jasinski of NASA\u2019s Jet Propulsion Laboratory in Southern California is the lead author of the new work published in Nature Astronomy<\/em> on November 11, 2024. Jasinski said: <\/p>\n
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If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus. The spacecraft saw Uranus in conditions that only occur about 4% of the time.<\/p>\n<\/blockquote>\n
What\u2019s a magnetosphere?<\/h3>\n
Magnetospheres serve as protective bubbles around planets (including Earth) with magnetic cores and magnetic fields. They shield worlds from jets of ionized gas \u2014 or plasma \u2014 that stream out from the sun in the solar wind. Learning more about how magnetospheres work is important for understanding our own planet. And it\u2019s also important to understand worlds in seldom-visited corners of our solar system and beyond.<\/p>\n
That\u2019s why scientists were eager to study Uranus\u2019 magnetosphere. And what they saw in the Voyager 2 data in 1986 flummoxed them. Inside the planet\u2019s magnetosphere were electron radiation belts with an intensity second only to Jupiter\u2019s notoriously brutal radiation belts. But there was apparently no source of energized particles to feed those active belts. In fact, the rest of Uranus\u2019 magnetosphere was almost devoid of plasma.<\/p>\n
The missing plasma also puzzled scientists because they knew that the five major Uranian moons in the magnetic bubble should have produced water ions, as icy moons around other outer planets do. They concluded that the moons must be inert with no ongoing activity.<\/p>\n
![\"Side-by-side](\"https:\/\/earthsky.org\/upl\/2024\/11\/Uranus-magnetosphere-NASA-JPL-Caltech-scaled-e1731431153283.jpg\")
View larger. | The first panel of this artist\u2019s concept depicts how Uranus\u2019s magnetosphere \u2014 its protective bubble \u2014 was behaving before the flyby of NASA\u2019s 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. Image via NASA\/JPL-Caltech.<\/figcaption><\/figure>\n Solving the mystery at Uranus<\/h3>\n
So why didn\u2019t we observe plasma? And what was happening to beef up the radiation belts? The new data analysis points to the solar wind. When plasma from the sun pounded and compressed the magnetosphere, it likely drove plasma out of the system. The solar wind event also would have briefly intensified the dynamics of the magnetosphere, which would have fed the belts by injecting electrons into them.<\/p>\n
The findings could be good news for those five major moons of Uranus: Some of them might be geologically active after all. With an explanation for the temporarily missing plasma, researchers say it\u2019s plausible that the moons actually may have been spewing ions into the surrounding bubble all along.<\/p>\n
Planetary scientists are focusing on bolstering their knowledge about the mysterious Uranus system, which the National Academies\u2019 2023 Planetary Science and Astrobiology Decadal Survey prioritized as a target for a future NASA mission.<\/p>\n
New studies of Uranus<\/h3>\n
JPL\u2019s Linda Spilker was among the Voyager 2 mission scientists glued to the images and other data that flowed in during the Uranus flyby in 1986. She remembers the anticipation and excitement of the event, which changed how scientists thought about the Uranian system.<\/p>\n
Spilker, who has returned to the iconic mission to lead its science team as project scientist, said: <\/p>\n
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The flyby was packed with surprises, and we were searching for an explanation of its unusual behavior. The magnetosphere Voyager 2 measured was only a snapshot in time. This new work explains some of the apparent contradictions, and it will change our view of Uranus once again.<\/p>\n<\/blockquote>\n
Voyager 2, now in interstellar space, is almost 13 billion miles (21 billion km) from Earth.<\/p>\n
Bottom line: A new analysis of data shows that when the Voyager 2 spacecraft flew past Uranus in 1986, it saw a skewed view of the planet\u2019s magnetosphere because a large solar wind event had just buffeted Uranus.<\/p>\n
Source: The anomalous state of Uranus\u2019s magnetosphere during the Voyager 2 flyby<\/p>\n
Via NASA\/JPL-Caltech<\/p>\n
Read more: Evidence for ocean on Uranus moon Miranda is a surprise<\/p>\n
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\n - The magnetosphere showed intense electron radiation belts<\/strong> but no source of energized particles to feed those active belts.<\/li>\n