Science Frontiers ONLINE No. 18: Nov-Dec 1981 Issue Contents

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Phoebe Not Locked To Saturn

When Voyager 2 passed through the Saturn system a few months ago, it snapped pictures of Phoebe, Saturn's outermost moon. Phoebe is nicely rounded, 200 kilometers in diameter, and swings around Saturn in a retrograde orbit 550 days long -- nothing anomalous so far. Phoebe, however, turns out to be the only solar-system satellite whose axial period of rotation is not about equal to its period of rotation about its parent planet. All other moons, including our own, are gravitationally "locked" so that they always point the same hemisphere at the parent planet.

(Anonymous; "Voyager's Fleeting Glimpse of Phoebe," New Scientist, 91:779, 1981.)

Comment. One inference here is that Phoebe is a relatively recent addition -- and a good-sized one -- to the Saturn system, and just hasn't been there long enough to become "locked."

From Science Frontiers #18, NOV-DEC 1981. © 1981-2000 William R. Corliss

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Science Frontiers Sourcebook Project Reviewed in: Icarus: Volume 41, Issue 3, p. 470-470 1984, Vol.56:3, P.615 1983, Vol.58:3 June 1984, Vol.60:3 Dec 1984, Vol.72:3 Dec 1987 Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 1987 American Journal of Physics, Volume 52, Issue 8, p. 764 August 1984 Quotes "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada>, Vol. 81, no. 1 (1987), p. 24., 02/1987