Saturn: Hubble provides clear images of the planet's aurora | PIA01269 | ||
![]() |
This is the first image of Saturns ultraviolet aurora taken by the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope in October 1997, when Saturn was a distance of 1.3 billion kilometers from Earth. | ||
Go to Full Text | |||
![]() |
|||
![]() |
|||
Image Credit: Space Telescope Science Institute, J.T. Trauger (Jet Propulsion Laboratory) & NASA | |||
|
|||
This
is the first image of Saturns ultraviolet aurora taken by the Space Telescope
Imaging Spectrograph (STIS) on board the Hubble Space Telescope in October
1997, when Saturn was a distance of 1.3 billion kilometers from Earth. The
new instrument, used as a camera, provides more than ten times the sensitivity
of previous Hubble instruments in the ultraviolet. STIS images reveal exquisite
detail never before seen in the spectacular auroral curtains of light that
encircle Saturns north and south poles and rise more than a thousand miles
above the cloud tops. Saturn's auroral displays are caused by an energetic wind from the Sun that sweeps over the planet, much like the Earths aurora that is occasionally seen in the nighttime sky and similar to the phenomenon that causes fluorescent lamps to glow. But unlike the Earth, Saturn's aurora is only seen in ultraviolet light that is invisible from the Earth's surface, hence the aurora can only be observed from space. New Hubble images reveal ripples and overall patterns that evolve slowly, appearing generally fixed in our view and independent of planet rotation. At the same time, the curtains show local brightening that often follow the rotation of the planet and exhibit rapid variations on time scales of minutes. These variations and regularities indicate that the aurora is primarily shaped and powered by a continual tug-of-war between Saturn's magnetic field and the flow of charged particles from the Sun. |
![]() |
Study
of the aurora on Saturn had its beginnings just seventeen years ago. The
Pioneer 11 spacecraft observed a far-ultraviolet brightening on Saturns
poles in 1979. The Saturn flybys of the Voyager 1 and 2 spacecraft in the
early 1980s provided a basic description of the aurora and mapped for the
first time planets enormous magnetic field that guides energetic electrons
into the atmosphere near the north and south poles. The first images of Saturns aurora were provided in 1994-5 by the Hubble Space Telescopes Wide Field and Planetary Camera (WFPC2). Much greater ultraviolet sensitivity of the new STIS instrument allows the workings of Saturns magnetosphere and upper atmosphere to be studied in much greater detail. These Hubble aurora investigations provide a framework that will ultimately complement the in situ measurements of Saturns magnetic field and charged particles by NASA/ ESAs Cassini spacecraft, now en route to its rendezvous with Saturn early in the next decade. Two STIS imaging modes have been used to discriminate between ultraviolet emissions predominantly from hydrogen atoms (shown in red) and emissions due to molecular hydrogen (shown in blue). Hence the bright red aurora features are dominated by atomic hydrogen, while the white traces within them map the more tightly confined regions of molecular hydrogen emissions. The southern aurora is seen at lower right, the northern at upper left. |
|
Return to top of page |