Jay T. Bergstralh

Alan William Harris

United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch

The orbital motion of Triton was redetermined from photographic data spanning the interval 1899-1981. The resulting ephemeris should provide Triton positions with respect to Neptune with an accuracy of plus or minus 500 km through the end of the century. The following physical results follow from the orbit solution. The inverse mass of Neptune + Triton is solar mass over (cN + mT) = 19490 plus or minus 40. No acceleration of the mean motion nor orbital eccentricity were detected, thus constraining the tidal dissipation factors of Neptune and Triton to ON less than or equal to 650 and QT less than or equal to 10,000. Tidal heating of Triton is presently insignificant. The gravitational harmonic J2 of Neptune is 0.0043 plus or minus 0.0003 if Triton is as massive as mT/ MN = 0.00128, and if Neptune's spin is prograde with P approximately 18(h), or J2 = 0.0037 plus or minus 0.0002 if Triton is much less massive. Triton undergoes extreme climatic variations due to the combined motion of it's orbit plane and Neptune's orbital motion. Approximately 10% of Triton's surface is presently hidden from diurnal insolation, which may provide a powerful cold trap for atmospheric voltatiles.

Physical Properties of Neptune and Triton Inferred from the Orbit of Triton

Mildred Shapley Matthews

Ellis D. Miner

Uranus occupies a unique niche in the history of western thought; for while the planets from Mercury to Saturn had been known since pre-antiquity, Uranus was the first to be discovered, in 1781, through scientific investigation. Contemporary investigation of Uranus culminated in the Voyager 2 encounter in 1986. The results of that achievement, as well of concurrent research on the planet, are reviewed by 84 international authorities in this massive volume. Because Uranus' remoteness has prevented its being studied as intensively by earth-based observation as have other members of the solar system, most of what is known about the planet—its magnetic field and magnetosphere and satellites—were learned from the Voyager data, which is viewed here from a variety of perspectives. While the book is intended to serve as a comprehensive review, it also reports a substantial amount of original research results not previously published.

Jay T. Bergstralh

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