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FOR RELEASE: October 10, 1995
RELEASE NO.: STScI-PRC95-39
The aurora is produced as trapped charged particles precipitating from the magnetosphere collide with atmospheric gases -- molecular and atomic hydrogen in Saturn's case. As a result of the bombardment, Saturn's gases glow at far-ultraviolet wavelengths (110-160 nanometers) which are absorbed by the Earth's atmosphere, and so can only be observed from space-based telescopes. Saturn's magnetic field is nearly perfectly aligned with the planet's rotation, giving the auroral "ring" its symmetry centered on the pole. (The southern aurora is faintly visible in this view despite the fact that Saturn's northern pole is now tilted slightly toward Earth.)
The Hubble images demonstrate our capability to record from the Earth the auroral brightness and distribution about Saturn's poles, which will ultimately complement the in situ measurements of Saturn's magnetic field and charged particles to be made by the NASA/ESA Cassini spacecraft near the turn of the century.
Study of the aurora on Saturn had its beginnings a few decades ago. The Pioneer 11 probe observed a far-ultraviolet brightening on Saturn's poles in 1979. Beginning in 1980, a series of spectroscopic observations by the International Ultraviolet Explorer (IUE) have sporadically detected emissions from Saturn's auroral zones. The Saturn flybys of the Voyager 1 and 2 spacecraft, in the early 1980s, found auroral emissions confined to a circumpolar ring.
(Bottom) - For comparison, this is a visible-light color composite image of Saturn as seen by Hubble on December 1, 1994. Unlike the ultraviolet image, Saturn's familiar atmospheric belts and zones are clearly seen. The lower cloud deck is not visible at UV wavelengths because sunlight is reflected from higher in the atmosphere.
Credits: J.T. Trauger (JPL), J.T. Clarke (Univ. of Michigan), the WFPC2 science team, and NASA
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