When the Voyager 2 spacecraft became the first and only mission to fly by Uranus in 1986, it defined the way astronomers understand the ice giant. But the data collected by the probe also introduced new mysteries that have continued to intrigue scientists in the decades since the historic flyby.
Now, a new analysis of the data has revealed that Voyager 2 happened to pass by the distant planet during a rare event, suggesting that scientists’ current understanding of the planet may have been shaped — and distorted — by an unusual stellar coincidence.
The results of the study, published on Monday (11) in the journal , may have resolved some of the enigmas created by Voyager 2’s strange readings.
“The spacecraft saw Uranus under conditions that only occur about 4% of the time,” said study lead author Jamie Jasinski, a space plasma physicist at the Jet Propulsion Laboratory in Pasadena, California, in a statement.
The study’s results may also reinforce the idea that Uranus remains a largely misunderstood world, given that astronomers’ basic knowledge of the planet arose from an extraordinary anomaly.
A planet of peculiarities
The 2nd flyby of sideways-rotating Uranus revealed previously unknown rings and moons around the planet.
But the spacecraft’s observations of Uranus’ magnetosphere were very different from astronomers’ expectations, and scientists considered the planet an outlier among our solar system’s other large planets, such as Jupiter, Saturn and Neptune.
Magnetospheres are the protective bubbles around planets like Earth that have magnetic cores and magnetic fields, and are driven by the planet’s magnetic field. These magnetic bubbles protect planets from the solar wind, a stream of energetic particles and gas that continually flows from the sun.
Understanding how magnetospheres work around other planets not only helps scientists plan exploratory missions, but also provides insight into how Earth’s magnetosphere works.
Voyager 2 data showed that Uranus’s magnetosphere was home to unexpectedly powerful electron radiation belts. Its intensity was similar to the huge bands of radiation found around Jupiter.
As the largest planet in our solar system, Jupiter has a magnetic field 20,000 times stronger than Earth’s, according to NASA. The magnetic field captures charged particles and accelerates them to high speeds. The fast-moving particles release energy in the form of intense radiation that bombards Jupiter’s closest moons.
However, there was no apparent source of energetic particles to drive and increase the intensity of the belts seen around Uranus, as there appeared to be a lack of plasma, or ionized gas, which was strange because plasma is a common element in magnetospheres. around other planets.
Voyager 2’s observations of Uranus’s magnetosphere have challenged the way astronomers understand how magnetic fields trap energetic particles and their radiation.
Astronomers were perplexed by the lack of plasma because five of Uranus’s icy moons exist within the magnetosphere and should be producing ions within the magnetic bubble surrounding Uranus and some of its moons. This strange discovery led Voyager scientists to conclude that the moons must be completely inactive.
But a new analysis of Voyager 2 data showed that Uranus experienced a rare cosmic occurrence just before the flyby.
Solar interference
Days before the flyby, an intense solar wind event was released from the sun, shaking up space weather across the solar system. The solar wind hit Uranus and dramatically compressed its magnetosphere, likely pushing plasma out of it. But the solar event also made Uranus’ magnetosphere more dynamic by feeding it electrons, which boosted the planet’s radiation belts, according to the new study.
“If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere on Uranus,” said Jasinski.
It’s likely that Uranus’s magnetosphere would have a similar appearance to the magnetic bubbles around the other giant planets in our solar system without any anomalies, the study authors said.
The findings also suggest that some of Uranus’s moons may be geologically active, as they were likely releasing ions into the magnetosphere before the solar wind temporarily removed them.
“We highlight that our understanding of the Uranus system is highly limited, and our analysis shows that any conclusions drawn from the Voyager 2 flyby are equally uncertain,” the authors wrote in their study. “We suggest that the discoveries made by the Voyager 2 flyby should not be attributed to any typicality with respect to Uranus’ magnetosphere.”
The Uranus flyby “was full of surprises” and researchers immediately began looking for a way to explain the unexpected data, said Linda Spilker, project scientist for the twin Voyager probes at JPL, who served as one of the mission scientists for Voyager. 2 during this period. Spilker was not involved in the new study.
“The magnetosphere measured by Voyager 2 was just a snapshot in time,” Spilker said in a statement. “This new work explains some of the apparent contradictions and will change our view of Uranus once again.”
See also: NASA finds signs of voluminous and choppy rivers on Mars
