Composite Hubble Space Telescope image of aurorae (bright blue) encircling Saturn's north pole. Aurora are produced by the interaction of the solar wind with a planet's atmosphere. Charged particles collide with rarefied gases in the atmosphere, causing them to emit light. Because Saturn's atmosphere is dominated by hydrogen much of the light is emitted in the ultraviolet range. On Saturn, as on Earth, aurorae occur in polar regions. This is because the magnetic field of the planet channels the charged particles to these regions. There are two peaks (white) in the brightness of the aurorae, at dawn and just before midnight. This image is a composite of optical observations of Saturn made in early 2018 and ultraviolet observations of the auroras taken using Hubble's Space Telescope Imaging Spectrograph made over seven months in 2017.
October 15th, 2019
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