Saturn wears the crown
Hubble imaging reveals the majesty of a massive planet’s massive aurora.
For a period of seven months in 2017, NASA’s Hubble Space telescope took a series of images, using ultraviolet light, of auroras flickering around the north pole of Saturn.
The aurora is formed in a similar way to those seen at the high northern and southern latitudes on Earth, but with one crucial difference.
Electrically charged particles in the form of solar wind smash into each planet’s magnetosphere, which resists most of them but traps a certain percentage. These then interact with the magnetic field, and follow lines heading to the magnetic poles.
In Saturn’s case, however, the atmosphere comprises mainly hydrogen, which means the resulting auroras can’t be seen in the visible light spectrum, and become apparent only when observed at ultraviolet wavelengths. This required the use of Hubble’s Space Telescope Imaging Spectrograph.
This image, compiled by NASA and partner agencies, is a composite arising from the craft’s observations taken before and after the planet’s northern solstice.
The Hubble exercise was conducted at the same time as the Cassini probe was in the last act of its life, also imaging Saturn’s auroras.
The combined data is analysed in a paper published in the journal Geophysical Research Letters.