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Jupiter's unusual X-ray auroras

An infrared image of Jupiter's southern aurora from NASA's Juno spacecraft. Photo: NASA / JPL / Caltech / SwRI / ASI / INAF / JIRAM

Scientists report today they've detected X-ray auroras on Jupiter's southern pole that, unlike Earth's synchronized Northern and Southern Lights, behave independently from their northern counterparts. Exactly how the planet's magnetic field produce its powerful auroras is unknown.

The big picture: Aurora-producing magnetic fields protect life on Earth's surface so scientists want to be able to recognize their various features and processes as they search for places that could harbor life, study co-author William Dunn from University of College London told the Verge.

How they saw it: Using data collected in 2007 and 2016 from two space-based observatories that could see both poles at the same, William Dunn and his colleagues at University College London found Jupiter's southern aurora pulsed every 9-11 minutes whereas the northern one was inconsistent — it flared every 12, 26 or 40-45 minutes — and with varying brightness.

On Earth auroras form when charged particles in the solar wind get pushed to the planet's poles by the magnetic field. There, the particles collide with oxygen and nitrogen in the atmosphere and emit photons that we see as the Northern and Southern Lights. (There are also auroras in infrared light, ultraviolet light and X-ray that we can't see.) Earth's auroras brighten and dim together as the charged particles are pushed to each pole. Unexpectedly, Jupiter's auroras aren't in such unison.

Why it happens: Unclear but one possibility the researchers propose is that when the solar wind hits Jupiter's large and strong magnetic field, the lines vibrate and produce waves. Charged particles — some of which come from volcanic eruptions on Jupiter's moon Io and others from the solar wind — may ride those waves to the poles and collide with the atmosphere in X-ray producing pulses.

What's next: NASA's Juno spacecraft is orbiting Jupiter and sending data about the planet's magnetosphere. Researchers plan to combine that with X-ray observations to see how the aurora are connected to what is happening on the planet and whether the behavior they saw is common or an exception.

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