Alien aurorae on Uranus
Ever since Voyager 2 beamed home spectacular images of the planets in the 1980s, planet-lovers have been hooked on extra-terrestrial aurorae. Aurorae 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 powerful magnetic fields and are channelled into the upper atmosphere, where their interactions with gas particles, such as oxygen or nitrogen, set off spectacular bursts of light.
More information: www.spacetelescope.org/images/potw1714a/
Credit:
ESA/Hubble & NASA, L. Lamy