Jupiter turns blue before in-depth exam
Swirling bright streaks in this Jupiter aurora are the
footprints of three large moons
(CNN) -- An electric-blue aurora glows in this Hubble Space Telescope image of the atmosphere of Jupiter, released this week as the orbiting telescope and deep space probes prepare for the most extensive close-up study ever of the gas giant.
Like on Earth, the polar areas of Jupiter regularly experience auroras, which take place as electrons speed along the planet's magnetic field, exciting atmospheric gases and causing them to glow.
But the jovian light plumes exhibit some striking differences from their terrestrial counterparts. Swirling bright trails in this Jupiter aurora image reveal the footprints of three large moons.
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Io, Ganymede and Europa are responsible for the dazzling aurora streaks. Electric currents from the satellites generate emissions that flow along Jupiter's magnetic field, bolting in and out of the planet's upper atmosphere.
The Hubble observatory snapped this ultraviolet image in November 1998. NASA astronomers, who released this picture Thursday, have been re-examining many scientific images of auroras on Jupiter in advance of the first joint spacecraft investigation of the planet. Two NASA probes begin two weeks of flyby observations of the planet late this week.
Galileo has orbited the Jupiter system for five years. The newly arrived Cassini should fly to within 6 million miles (10 million km) of Jupiter on December 30. It will receive a boost from the planet's gravity as it continues toward its final destination, Saturn.
Before it leaves the Jupiter system, it will take pictures of the planet's night-side aurora in January. At the same time, back in Earth orbit, the Hubble telescope will train its powerful lens on Jupiter's day-side aurora.
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Space Telescope Science Institute
Hubble Heritage Project
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