Title:              Long-term changes in the semimajor axes of the outer
                    planets
Authors:            MILANI, A.; NOBILI, A. M.; FOX, K.; CARPINO, M.
Affiliation:        AB(Queen Mary College, London, England; Pisa,
                    Universita, Italy) AC(Queen Mary College, London,
                    England) AD(CNR, Centro Nazionale Universitario di
                    Calcolo Elettronico, Pisa, Italy)
Journal:            Nature (ISSN 0028-0836), vol. 319, Jan. 30, 1986, p.
                    386-388. SERC-NATO-CNR-supported research.
Publication Date:   01/1986
Origin:             STI
Category:           Astronomy
NASA/STI Keywords:  CELESTIAL MECHANICS, GAS GIANT PLANETS, NEPTUNE
                    (PLANET), ORBITAL ELEMENTS, PLUTO (PLANET), SECULAR
                    VARIATIONS, SOLAR ORBITS, URANUS (PLANET), LONG TERM
                    EFFECTS, NUMERICAL INTEGRATION, ORBIT CALCULATION,
                    ORBIT PERTURBATION
Bibliographic Code: 1986Natur.319..386M

Abstract

A 9.3 Myr numerical integration of the orbits of the outer planets has been performed using a pure Newtonian point mass model. An accurate integrator and an effective low-pass filtering of the output permitted high-order variations in the energies, and hence also in the semimajor axes, to be detected with periods ranging from tens of thousand to millions of years. The most interesting feature is an energy exchange between Uranus and Neptune with a period of 1,119,000 years, the same as the period of the libration between the perihelia of Jupiter and Uranus. The mechanism involves Jupiter and also Saturn, whose energy shows puzzling longer-term trends. The energy of Pluto changes mostly with periods close to that of the 3:2 libration in mean motion with Neptune. Its spectrum in this region shows a very complicated structure, but no indication of chaotic behavior is found.

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