NASA’s Hubble Space Telescope has captured rather awesome images of aurorae on Uranus, the second outermost planet of our Solar System.
The images were taken in ultraviolet, and superimposed on an existing picture of the whole planet taken by the Voyager 2 spacecraft in 1986. The gas giant itself appears as a large blue ball, owing to large amounts of methane in its upper atmosphere.
In this latest research, a team led by the Paris Observatory tracked two bursts of solar wind traveling from the Sun to Uranus in 2012 and 2014. As the wind hit the planet, they used Hubble to monitor Uranus’ aurorae, and found they were the most intense they had ever been. Amazingly, they also found the first direct evidence that the aurorae rotate with the planet, and as a consequence rediscovered the planet’s long-lost magnetic poles.
Hubble also captured a view of the planet’s ring, which encircles the equator but appears to be going up and down because Uranus is on its side with respect to the rest of the Solar System.
We’ve seen aurorae on Uranus before, notably in 2011, but they appear particularly large in this latest view. Like on Earth, aurorae on Uranus are caused by streams of charged particles being caught by the planet’s magnetic fields. They are funneled into the poles, where they interact with gas particles like oxygen and nitrogen to give off bursts of light.
On Jupiter, which has an extremely powerful magnetic field, the aurorae are a permanent feature. In fact, just yesterday we found out that its aurorae may be driving a “Great Cold Spot” on the gas giant. We’ve seen aurorae on Saturn several times, too.
But we know much less about Uranus and its aurorae. We’ve only visited it once, thanks to a flyby by the aforementioned Voyager 2 spacecraft, so much is still unknown about the third largest planet in our Solar System and its moons. There are some interesting proposals knocking around to send an orbiter to Uranus in the future, though, so maybe we’ll learn more about this gas giant one day.