On June 11, 2004, Cassini came within 2,068 km (1,285 miles) of the dark moon 23 years after Voyager 2's remote flyby in 1981 at a distance of 2.2 million km (1.4 million miles), 1,000 times further away.
When it was discovered in 1898, Phoebe was Saturn's outermost known moon. That changed with the discovery of several smaller moons in 2000. Phoebe is almost four times farther from Saturn than its nearest major neighbor, Iapetus, and substantially larger than any of the other moons orbiting at comparable distances. With a diameter of 220 km (140 miles), it rotates on its axis every 9 hours 16 minutes and completes a full orbit around Saturn in about 18 months. All of Saturn's moons except for Phoebe and Iapetus orbit very nearly in the plane of Saturn's equator. Phoebe's orbit is highly eccentric and retrograde: it orbits backwards with respect to the direction of the other moons.
Based on data from the Voyager flyby, Phoebe resembles a sort of dark asteroid. It may be very primitive. All previous indications suggest that it may be a captured Kuiper Belt object, one of the millions of asteroid-like bodies from outside the orbit of Pluto. If this is the case, the images of it sent back by Cassini in 2004 represent the most detailed close-ups of any such object ever taken.
Related entry Saturn, moons
Related category PLANETS AND MOONS
Archived newsPhoebe moon may be captured comet (May 5, 2005)
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