Ken Moscati and Abi Rymer, JHUAPL
This artist's concept shows a glowing patch of ultraviolet light near Saturn's north pole that occurs at the "footprint" of the magnetic connection between Saturn and its moon Enceladus. The magnetic field lines and the footprint were detected by the ultraviolet imaging spectrograph and fields and particles instruments on board NASA's Cassini spacecraft.
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updated 4/20/2011 2:03:21 PM ET 2011-04-20T18:03:21

A shimmering patch of light as big as Sweden detected at the north pole of Saturn is the spectacular result of a giant stream of electrically charged particles from the planet's moon Enceladus, scientists find.

On Earth, surges of charged particles from the sun colliding with our planet's magnetic field create the northern and southern lights, or auroras. Similar patches of light have been seen on Jupiter, caused by electrons and ions originating from that planet's volcanically active moon Io.

Saturn also has its own aurora light show, which is created when solar particles from the sun interact with the planet's magnetic field. The new study, however, is the first time astronomers have caught a Saturn moon creating auroras on the ringed planet.

Enceladus is an extraordinarily active moon, with "ice volcanoes" (cryovolcanoes) that spray water vapor and organic particles into space. Researchers had long suspected that would cause aurora-like spots on Saturn. However, space telescopes gazing at the ringed planet failed for years to find any evidence of such patches.

Now, using NASA's Cassini spacecraft in orbit around Saturn, researchers have finally detected signs of these lights.

The eruptions on Enceladus create a massive cloud of electrically charged plasma that shoots electrons and ions 150,000 miles along magnetic field lines to blast Saturn's north pole. The resulting spot of light measures about 750 miles by about 250 miles, covering an area slightly larger than California. Scientists compared it to Sweden.

At its brightest, the patch shines with an ultraviolet light far less intense than Saturn's polar aurora but comparable to the faintest Earth aurora visible without a telescope.

The scientists note this patch appears to vary in brightness by up to a factor of three, suggesting Enceladus spews out matter at a very non-constant rate.

"The electron beams flicker with timescales on the order of minutes," said researcher Abigail Rymer, a Cassini team scientist based at Johns Hopkins University. "It is a very dynamic interaction."

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Although it remains unclear what specifically is driving the cryovolcano activity at Enceladus, "one thing is clear: Enceladus cannot vent at this rate forever," Rymer told Space.com. "Scientists have been wondering whether the venting rate is variable, and these new data suggest that it is."

The scientists detailed their findings in the April 21 issue of the journal Nature.

Follow Space.com contributor Charles Q. Choi on Twitter @cqchoi. Visit Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Photos: Best of Cassini

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  1. Starring Saturn

    This backlit view of Saturn was voted the favorite image to come from the Cassini orbiter - and it has been described as "perhaps the most stunning photograph ever taken." The image, captured on Sept. 15, 2006, shows two faint rings that were discovered by the Cassini team. And at the highest resolution, Earth itself appears as a pale blue dot just to the left of the brightest rings, at about the 10 o'clock position. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  2. Dark rings

    An infrared image from the Cassini orbiter, acquired May 24, 2007, reveals clouds beneath the hazes in Saturn's atmosphere, as well as the unilluminated side of the giant planet's rings. The shadows of the rings fall upon the planet's cloud layer. This image shares the honors as the favorite black-and-white picture from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  3. Abstract art

    A Cassini image from May 10, 2006, shows the shaded edge of Saturn's disk, rounded by dark rings seen nearly edge-on. The crescent disk of Titan, Saturn's largest moon, can be seen in the background beyond the rings. This image shares the honors as the favorite black-and-white image from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  4. Pearly moons

    Two of Saturn's moons - Tethys and Enceladus - look like pearls backdropped by the planet's disk in this image, captured on July 24, 2007. The thin "string" connecting the pearls is actually the plane of the planet's rings, seen edge-on. The rings cast a dark shadow on Saturn's disk. Two other moons appear in this image, although they can barely be made out at the highest resolution: Hyperion is near the lower left corner of the image, and Epimetheus is the slightest of specks between Tethys and Enceladus. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  5. Saturn from on high

    The Cassini spacecraft provides a high-contrast view of Saturn and its rings, as seen from above. This portrait is actually a mosaic of 36 images taken on Jan. 19, 2007, from about 40 degrees above the plane of the rings. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  6. Shadows on clouds

    Saturn's darkened rings cast shadows on the planet's blue and gold cloud tops, while the moon Dione hangs like a dot in the black sky beyond. This image was taken by the Cassini spacecraft on Feb. 4, 2007, from a distance of about 800,000 miles. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  7. View from below

    Cassini coasts beneath giant Saturn, staring upward at its gleaming crescent and icy rings. A great bull's-eye pattern is centered on the south pole, where a vast, hurricane-like storm spins. This view, obtained on Jan. 30, 2007, looks toward the lit side of the rings from about 26 degrees below the ring plane. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  8. Pastel planet

    Dark and sharply defined ring shadows appear to constrict the flow of color from Saturn's warmly hued south to the bluish northern latitudes. Scientists studying Saturn are not yet sure about the precise cause of the color change from north to south. The different colors may be due to seasonal effects on the atmosphere. The images that went into this mosaic were obtained by the Cassini spacecraft on Feb. 4, 2007. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  9. Ringing success

    This ultraviolet image from the Cassini spacecraft shows the detailed composition of Saturn's outer C and inner B rings from left to right, with the inner B ring beginning a little more than halfway across the image. The general pattern is from "dirty" red particles to the denser ice shown in turquoise as the ringlets spread outward. (University Of Colorado, LASP / AP) Back to slideshow navigation
  10. A is for amazing

    This ultraviolet image shows the A ring, beginning with a 'dirty' interior of red followed by a general pattern of more turquoise as it spreads away from the planet, indicating a denser material made up of ice. The red band roughly three-fourths of the way outward in the A ring is known as the Encke gap. (University Of Colorado, LASP - NASA / Reuters) Back to slideshow navigation
  11. Casting a shadow

    This image taken by Cassini shows the planet Saturn casting a shadow over its rings. (NASA - JPL - Caltech / Reuters) Back to slideshow navigation
  12. Titan revealed

    This is an infrared image of Titan, one of Saturn's moons, mapping the surface hidden beneath the moon's opaque atmosphere. Green areas represent water ice, while yellow areas have higher concentrations of hydrocarbons. The white spot is a methane cloud. (NASA) Back to slideshow navigation
  13. Ripples in the ring

    Scallops in the ring on the left side of this image were likely caused by a Saturnian moon rolling along the edge. One bright ringlet is visible within the gap, and at least one other faint ringlet can be made out. "This is textbook ring physics, right there, in one image," says Cassini imaging team leader Carolyn Porco. (NASA - SSI) Back to slideshow navigation
  14. Wisps in space

    A close-up of one of Saturn's rings shows a wispy pattern of ripples that may have been stirred up by a moonlet's orbit. Such unprecedented views of ring details are possible because of the Cassini camera's resolution. (NASA TV) Back to slideshow navigation
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