An X-ray aurora has been detected at Jupiter’s South Pole, reports a paper published online this week in Nature Astronomy. The study shows that the long-sought southern aurora, contrary to expectations, behaves independently of its northern counterpart, questioning our current understanding of how X-ray auroras are generated on the planet.

Auroras are planetary phenomena that occur when the energetic particle wind from a star interacts with the magnetic field (magnetosphere) of a planet, and usually appear at the magnetic poles. Jupiter, with its intense magnetosphere, hosts extensive and strong auroras, particularly visible in the X-rays. However, up until now, only the northern hot spot had been detected.

William Dunn and colleagues detected the southern X-ray auroral hot spot of Jupiter and studied its behaviour using observations taken from two space observatories - XMM-Newton and Chandra - in 2007 and 2016. Surprisingly, the northern and the southern X-ray hot spots pulsate at different frequencies and intensities.

These results were not predicted by current models for how Jupiter’s auroras are generated. The authors suggest several possible explanations for this behaviour; however, observations from the NASA Juno spacecraft, currently orbiting Jupiter, will help to discriminate between the proposed mechanisms.