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Astronomie - HUBBLE SIEHT AURORA AUF SATURN

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Astronomers using the NASA/ESA Hubble Space Telescope have captured new images of the dancing auroral lights at Saturn’s north pole. Taken in April and May 2013 from Hubble’s perspective in orbit around Earth, these observations provide a detailed look at previously unseen dynamics in the choreography of the auroral glow.
The ultraviolet images, taken by Hubble’s super-sensitive Advanced Camera for Surveys, capture moments when Saturn’s magnetic field is affected by bursts of particles streaming from the Sun.
Saturn’s magnetosphere – the vast magnetic ‘bubble’ that surrounds the planet – is compressed on the Sunward side of the planet, and streams out into a long ‘magnetotail’ on the nightside.
It appears that when particles from the Sun hit Saturn, the magnetotail collapses and later reconfigures itself, an event that is reflected in the dynamics of its auroras.
Saturn was caught during a very dynamic light show – some of the bursts of light seen shooting around Saturn’s polar regions travelled more than three times faster than the speed of the gas giant’s roughly 10-hour rotation period!
The new observations were taken as part of a three-year Hubble observing campaign, and are presented in a paper published in the journal Geophysical Research Letters. The images complement those taken by the international Cassini spacecraft orbiting Saturn.
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These images reveal the dynamic nature of Saturn’s aurorae. Viewing the planet's southern polar region for several days, NASA's Hubble Space Telescope snapped a series of photographs of the aurora dancing in the sky. The snapshots show that Saturn's aurorae differ in character from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared with Earth, where auroral storms develop in about 10 minutes and may last for a few hours, Saturn's auroral displays always appear bright and may last for several days.
The observations, made by Hubble and the Cassini spacecraft, while en route to the planet, suggest that Saturn's auroral storms are driven mainly by the pressure of the solar wind - a stream of charged particles from the Sun - rather than by the Sun's magnetic field.
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On 24 February 2009, the NASA/ESA Hubble Space Telescope captured a photo sequence of four moons of Saturn passing in front of their parent planet. This picture was taken at 13:12 CET (12:12 UT). The moons, from far left to right, are the white icy moons Enceladus and Dione, the large orange moon Titan, and icy Mimas. Due to the angle of the Sun, they are each preceded by their own shadow.
Quelle: ESA
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