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Rare Quadruple Transit
Rare Quadruple Transit
17 Mar 2009
(Source: NASA/JPL)

Color image of Saturn with four moons in front of it.
Saturn and its moons, Titan, Mimas, Dione and Enceladus.

PASADENA, Calif. -- On Feb. 24, 2009, NASA's Hubble Space Telescope took a photo of four moons of Saturn passing in front of their parent planet. The pictures were taken by the Wide Field and Planetary Camera 2, developed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

In the new view, the giant orange moon Titan casts a large shadow onto Saturn's north polar hood. Below Titan, near the ring plane and to the left, is the moon Mimas, casting a much smaller shadow onto Saturn's equatorial cloud tops. Farther to the left, and off Saturn's disk, are the bright moons Dione and the fainter Enceladus.

These rare moon transits only happen when the tilt of Saturn's ring plane is nearly "edge on" as seen from Earth. Saturn's rings will be perfectly edge on to our line of sight on Aug. 10, 2009, and Sept. 4, 2009. Unfortunately, Saturn will be too close to the sun to be seen by viewers on Earth at that time. This "ring plane crossing" occurs every 14 to 15 years. In 1995 to 1996, Hubble witnessed the ring plane crossing event as well as many moon transits, and even helped discover several new moons of Saturn.

The banded structure in Saturn's atmosphere is similar to Jupiter's.

Early 2009 was a favorable time for viewers with small telescopes to watch moon and shadow transits crossing the face of Saturn. Titan, Saturn's largest moon, crossed Saturn on four separate occasions: January 24, February 9, February 24, and March 12, although not all events were visible from all locations on Earth.

These pictures were taken with the Wide Field and Planetary Camera 2 on Feb. 24, 2009, when Saturn was roughly 1.25 billion kilometers (775 million miles) from Earth. Hubble can see details as small as 300 kilometers (190 miles) across on Saturn. The dark band running across the face of the planet slightly above the rings is the shadow of the rings cast on the planet.

For images, video, and more information, visit http://hubblesite.org/news/2009/12 and http://heritage.stsci.edu/2009/12.

The California Institute of Technology manages JPL for NASA.

Media contacts: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

Ray Villard 410-338-4514
Space Telescope Science Institute, Baltimore, Md.
villard@stsci.edu

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Last Updated: 18 Mar 2009