Hubble spots auroras on Uranus

April 10, 2017, NASA's Goddard Space Flight Center
This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble -- one for the ring and one for the auroras.Astronomers tracked the interplanetary shocks caused by two powerful bursts of solar wind traveling from the sun to Uranus, then used Hubble to capture their effect on Uranus' auroras -- and found themselves observing the most intense auroras ever seen on the planet. By watching the auroras over time, they collected the first direct evidence that these powerful shimmering regions rotate with the planet. They also re-discovered Uranus' long-lost magnetic poles, which were lost shortly after their discovery by Voyager 2 in 1986 due to uncertainties in measurements and the featureless planet surface. Credit: ESA/Hubble & NASA, L. Lamy / Observatoire de Paris

This is a composite image of Uranus by Voyager 2 and two different observations made by Hubble—one for the ring and one for the auroras.

Ever since Voyager 2 beamed home spectacular images of the in the 1980s, planet-lovers have been hooked on auroras on other planets. Auroras are caused by streams of charged particles like electrons that come from various origins such as solar winds, the planetary ionosphere, and moon volcanism. They become caught in and are channeled into the upper atmosphere, where their interactions with gas particles, such as oxygen or nitrogen, set off spectacular bursts of light.

The auroras on Jupiter and Saturn are well-studied, but not much is known about the auroras of the giant ice planet Uranus. In 2011, the NASA/ESA Hubble Space Telescope became the first Earth-based telescope to snap an image of the auroras on Uranus. In 2012 and 2014 a team led by an astronomer from Paris Observatory took a second look at the auroras using the ultraviolet capabilities of the Space Telescope Imaging Spectrograph (STIS) installed on Hubble.

They tracked the interplanetary shocks caused by two powerful bursts of solar wind traveling from the sun to Uranus, then used Hubble to capture their effect on Uranus' auroras—and found themselves observing the most intense auroras ever seen on the planet. By watching the auroras over time, they collected the first direct evidence that these powerful shimmering regions rotate with the planet. They also re-discovered Uranus' long-lost magnetic poles, which were lost shortly after their discovery by Voyager 2 in 1986 due to uncertainties in measurements and the featureless planet surface.

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Mark Thomas
5 / 5 (3) Apr 11, 2017
Uranus is the closest planet that no NASA spacecraft has orbited. The only fly-by of Uranus occurred in 1986 by Voyager 2, which itself was launched in 1977. It should be obvious to all concerned that a single fly-by with 1970s technology is barely scratching the surface of what we can learn there. The known mysteries include a bizarre offset magnetic field, extreme tilt, lack of internal heat and some very unusual moons (27 total plus rings). For example, Miranda is more than a little odd and Titania may have a subsurface ocean.

We need only to prioritize a Uranus Orbiter highly enough to make it happen. It is (or will be) doable. Perhaps much the same technology could be used for Neptune Orbiter too, doubling the value of the investment. Similarly, a return to Saturn would (essentially) triple the return on investment.

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