Uranus Ejected a Giant Plasma Bubble During Voyager 2's Visit

Uranus is unquestionably weird. Swirling with mostly water, methane and ammonia, the solar system’s seventh planet is tipped over at 98 degrees, so its magnetic poles take turns directly facing the sun. And its magnetic field is strangely misaligned with the planet’s rotation, causing it to wildly lurch about.

Back in 1986, the ice giant world got what remains its only visitor from Earth — Voyager 2, which is now more than 11 billion miles from Earth, but at that time flew a mere 50,600 miles above Uranus’s cloudy skies. As it passed, Voyager 2 heard an odd magnetic whisper, a signal so ephemeral that it went unnoticed.

More than three decades later, scientists were taking a deep dive into the venerable spacecraft’s data pool, hoping to find scientific mysteries that could help support a return mission to Uranus and its ice giant sibling, Neptune. They unearthed that magnetic hiccup, and realized it represented the detection of a mass of electrically excited gas with a width 10 times Earth’s circumference.

This ginormous bubble was a jettisoned part of Uranus’s atmosphere. Although only one was spotted, other gassy missiles may also be launched every 17 hours, the time it takes Uranus to complete one rotation.

https://www.nytimes.com/2020/03/27/science/uranus-bubble-voyager.html

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