Voyager 2 is the only craft to visit Uranus. Its findings may have misled us for 40 years.

• Much of our understanding of Uranus comes from Voyager 2's flyby, which to date remains the only time a spacecraft has visited the planet.
• Voyager 2's data on the magnetosphere surrounding Uranus has for decades left scientists perplexed.
• As a result, Uranus earned a decades-long reputation as an outlier in our solar system. But new research may be flipping that understanding on its head.

A lone spacecraft's visit to Uranus may have left us with the complete wrong impression of the ice giant for nearly 40 years.

The strange, sideways-rotating planet – the third largest in our solar system – has always been something of a mystery to astronomers. But when Voyager 2 got an up-close look at Uranus in 1986, scientists were able to glean some insights that, while confounding, at least shed some light on a crucial characteristic that seemed to set the planet apart from other giants like Jupiter.

Or so they thought.

A fresh look at the data collected during the Voyager 2 flyby revealed that the probe's visit to Uranus may have accidentally coincided with a rare interstellar event. The findings, published Monday in a study in the journal Nature Astronomy, suggest that our understanding of the planet's protective magnetic field, or magnetosphere, may be flawed.

“If Voyager 2 had arrived just a few days earlier, it would have observed a completely different magnetosphere at Uranus,” said lead study author Jamie Jasinski, a physicist at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement. “The spacecraft saw Uranus in conditions that only occur about 4% of the time.”

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Voyager 2 visited Uranus in 1986

Much of our understanding of Uranus comes from Voyager 2's flyby, which to date remains the only time a spacecraft has visited the planet.

The probe, along with its Voyager 1 twin, launched in 1977 from Cape Canaveral, Florida to explore the far reaches of our solar system. The probes, which continue to travel billions of miles away, have both reached interstellar space – Voyager 1 in 2012 and Voyager 2 in 2018, according to NASA.

But long before that, Voyager 2 stopped by Uranus, coming within 50,600 miles of Uranus's cloudtops. While encountering the planet on Jan. 24, 1986, the probe returned detailed photos and other data on the world, its moons, magnetic field and dark rings.

Why were scientists interested in Uranus' magnetosphere?

Voyager 2's data on the magnetosphere surrounding Uranus has, for decades, left scientists perplexed.

Magnetospheres provide a protective bubble around planets with magnetic cores and magnetic fields, shielding them from the sun's harmful flow of gas (or plasma) streaming out in solar winds. Scientists have long been interested in learning about the magnetospheres of other planets in hopes of better understanding Earth's own.

What made Uranus' magnetosphere so strange were its radiation belts with an unexpected intensity rivaling that of Jupiter's.

Just as mystifying was the absence of plasma. The energetic ionized particles are common to other planets’ magnetospheres, and scientists had theorized that the five major Uranian moons in the magnetic bubble should have produced them.

Instead, the Voyager 2 findings forced them to conclude that the moons must be inactive.

Solar wind may have skewed Voyager data: Study

As a result, Uranus earned a decades-long reputation as an outlier in our solar system.

Now, new research may be flipping that understanding on its head.

Though it was far from intentional, Voyager 2's flyby may have taken place at the same time that some unusual space weather was squashing the planet's magnetic field – skewing the probe's data. Solar winds pounding the magnetosphere would have temporarily driven plasma out of the system while also ratcheting up the power of the magnetosphere, according to the study.

So, instead of getting a full picture of Uranus, scientists back on Earth were presented with a misleading "snapshot in time," said Linda Spilker, project scientist for the twin Voyager probes at JPL, in a statement.

What that means is those five major moons of Uranus may be active after all.

“This new work explains some of the apparent contradictions, and it will change our view of Uranus once again," said Spilker, who served as one of the mission scientists for Voyager 2 during its visit.

Will NASA now revisit Uranus?

The study’s authors say their research highlights how little we know about Uranus and how critical future missions to the planet may be.

A 2022 report from the National Academies of Sciences, Engineering and Medicine called on NASA to make another mission to Uranus a priority in the next decade – something the space agency appears to have in the works.

In plans highlighted in a 2023 report from Scientific American, NASA would launch a spacecraft by 2032 that would orbit the planet and send a probe into its atmosphere.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com