Evrim Yazgin
Cosmos science journalist
Scientists have gone back over data to see that NASA’s Voyager 2 spacecraft’s flyby of Uranus occurred under rare planetary conditions which made it hard to probe.
The flyby occurred in 1986 and still provides much of the scientific understanding of the gas planet. The new paper published in Nature Astronomy suggests that Voyager 2 passed by Uranus when the planet’s magnetosphere was unusually suppressed by solar wind.
It might mean we understand less about Uranus than we thought.
Previous analysis of Voyager 2 data revealed Uranus’s magnetosphere was unique, with a highly asymmetrical shape and relative lack of plasma compared to the magnetospheres of other planets. It also had unusually intense belts of highly energetic electrons.
Researchers reanalysed the data from just before Voyager 2’s flyby and found that the probe’s data came from a period just after an intense solar wind event sent a stream of charged particles from the Sun’s atmosphere.
“Voyager 2 observed Uranus’s magnetosphere in an anomalous, compressed state that we estimate to be present less than 5% of the time,” the authors write.
The data suggests that the planet’s magnetosphere is actually similar to the other gas giants Jupiter, Saturn and Neptune.
Their analysis also suggests that it’s possible that Uranus’s moons Titania and Oberon may orbit outside the magnetosphere, allowing scientists to see if there are subsurface oceans on the moons.
Voyager 2 is the only spacecraft to have visited Uranus and Neptune. It was launched in 1977 and is currently more than 20 billion km from Earth – 2.5 times further than Pluto is from the Sun.
It is expected to keep operating into the late 2020s.
