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Uranus Auroras Glimpsed from Earth

For the first time, scientists have captured images of auroras above the gas giant Uranus. Unlike auroras on Earth, which can turn the sky greens and purples for hours, the newly detected auroras on Uranus are fainter and appeared to only last a couple minutes, detected twice on the dayside of Uranus.

The unfamiliar appearance of the auroras is due to Uranus’ rotational weirdness and peculiar traits of its magnetic axis, which is both offset from the center of the planet and lists at an angle of 60 degrees from the rotational axis. The magnetic field is thought to be generated by a salty ocean within the planet, resulting in the off-center magnetic axis.

Capturing the new images of Uranus’s auroras resulted from a combination of good luck and careful planning. In 2011, Earth, Jupiter and Uranus were lined up so that the solar wind could flow from the Sun, past Earth and Jupiter, and then toward Uranus. When the Sun produced several large bursts of charged particles in mid-September 2011, the researchers used Earth-orbiting satellites to monitor the solar wind’s local arrival two to three days later.

Two weeks after that, the solar wind sped past Jupiter at 500 kilometers per second (310 miles per second). Calculating that the charged particles would reach Uranus in mid-November, the team scrambled to scheduled time on the Hubble Space Telescope. »