When NASA’s Voyager 2 spacecraft flew by Uranus in 1986, planetary scientists were treated to their first ever close-up view of the ice giant planet.<\/p>

What’s more, Voyager 2 has been the only spacecraft to visit Uranus so far, meaning much of what scientists know about the planet has been gleaned from that fleeting encounter.<\/p>

More on Uranus<\/strong><\/strong><\/h3>

How Uranus was discovered<\/strong><\/em><\/a><\/li>
Webb’s wonderful image of Uranus<\/a><\/strong><\/em><\/li>
Why we need to send a spacecraft to Uranus<\/strong><\/em><\/a><\/li> <\/ul> <\/div>

Credit: NASA, ESA, CSA, STScI <\/figcaption> <\/figure> <\/div> <\/div>
The flyby also threw up some unexpected results, which a team of astronomers have now seemingly been able to solve by diving back into the data.<\/p>
Results have implications for our understanding of Uranus’s magnetosphere, and could mean its moons are more geologically active than thought.<\/p>
$\"A$
A shot of crescent Uranus captured by Voyager 2 on 25 January 1986 from a range of 600,000 miles. Credit: NASA <\/figcaption> <\/figure>
Voyager 2’s Uranus flyby<\/strong><\/h2> Uranus is a strange world. It rotates on its side and is the coldest planet<\/a> despite not being the furthest from the Sun.<\/p>
Planetary scientists don’t know as much about it as they do about, say, Mars or Jupiter, which have been extensively studied by rovers and orbiters.<\/p>
Voyager 2’s flyby revealed previously-unknown moons and rings around Uranus.<\/p>
It also detected energised particles at Uranus that seemed at odds with scientists’ understanding of how magnetic fields<\/a> work to trap particle radiation.<\/p>
This led to the idea that Uranus was something of a scientific anomaly in the Solar System.<\/p>
$\"Uranus's$
Uranus’s rings, as seen by the Voyager 2 spacecraft. Credit: NASA\/JPL <\/figcaption> <\/figure>
Astronomers have gone back to look at the Voyager 2 data and found this apparent anomalous data could have been sheer coincidence.<\/p>
In the days leading up to the flyby, Uranus was hit by a strange kind of space weather<\/a> that squashed the planet\u2019s magnetic field.<\/p>
This had the effect of compressing Uranus\u2019s magnetosphere.<\/p>
“If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus,” says Jamie Jasinski of NASA\u2019s Jet Propulsion Laboratory in Southern California, lead author of the study published in Nature Astronomy.<\/p>
“The spacecraft saw Uranus in conditions that only occur about 4% of the time.”<\/p>
$\"Uranus's$
Uranus’s moons Titania (left) and Oberon (right) in two images captured by Voyager 2. Moons are not to scale. Credit: NASA\/JPL <\/figcaption> <\/figure>
Something strange in Uranus’s magnetosphere<\/strong><\/h2>
A magnetosphere around a planet acts as a sort of protective shield, with a magnetic core and magnetic field.<\/p>
It protects the planet from the solar wind, a stream of charged particles emanating from the Sun.<\/p>
Earth’s magnetosphere, for example, helps protect us from these charged particles, and so understanding more about how they work is of vital importance.<\/p>
Voyager 2 found electron radiation belts within Uranus’s magnetosphere so intense, they would be bettered only by Jupiter’s radiation belts.<\/p>
But there was apparently no source of energised particles to feed the planet’s active belts.<\/p>
And scientists knew the five major moons around Uranus, in the magnetic bubble, should have been producing water ions, so concluded the moons must be inert with no ongoing activity.<\/p>
$\"Artist\u2019s$
Artist\u2019s impression. Left shows how Uranus\u2019s magnetosphere was behaving before the Voyager 2 flyby. Right shows solar weather during the 1986 flyby. Credit: NASA\/JPL <\/figcaption> <\/figure>
Mystery solved?<\/strong><\/h2>
New analysis of the data says when plasma from the Sun hit Uranus’s magnetosphere, it ejected plasma out of the system<\/p>
This solar wind event would have intensified the dynamics of the magnetosphere, strengthening the belts by injecting electrons into them.<\/p>
Having now explained the temporarily missing plasma, the team say the moons may have been ejecting ions into the surrounding bubble all along.<\/p>
This means some of Uranus’s moons could be geologically active after all.<\/p>
Linda Spilker of NASA’s Jet Propulsion Laboratory was among the Voyager 2 mission scientists who got first glimpse of the Uranus flyby data in 1986.<\/p>
“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,” says Spilker.<\/p>
“This new work explains some of the apparent contradictions, and it will change our view of Uranus once again.”<\/p>
www.jpl.nasa.gov<\/strong><\/a><\/p> <\/body><\/html>\n
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