The chaotic obliquity of the planets
Article Abstract:
The obliquity or spin-axis orientation of the inner or terrestrial planets, Mercury, Venus, Earth and Mars, has undergone chaotic variations in the planets' histories and Mars is still experiencing variations. Therefore, their obliquities cannot be considered primordial since they could have started with almost a zero obliquity that changed during the chaotic variation caused by their primordial spin rate. Mercury and Venus' obliquities have stabilized because of tidal dissipation while the Moon may have had the same effect on the Earth.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1993
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Orbital migration of the planetary companion of 51 Pegasi to its present location
Article Abstract:
The planetary companion orbiting the solar-type star 51 Pegasi probably formed at a distance from the star and then moved inwards. The companion was probably formed by an accumulation of solids and the capture of gas. The inward movement was due to its interactions with the remains of the circumstellar disk. The migration which probably stopped due to tidal interactions with the star resulted in an almost circular orbit. Analysis of the changes in its velocity suggests that its mass is similar to that of Jupiter.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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A resonance in the Earth's obliquity and precession over the past 20 Myr driven by mantle convection
Article Abstract:
The influence of mantle convection on the Earth's precession, obliquity and insolation parameters has been studied, using viscous flow theory. The convection-induced change in the Earth's flattening is found to perturb the main frequency of the Earth's precession into the resonance linked to a secular term in the orbits of Jupiter and Saturn, significantly affecting the Earth's obliquity.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1997
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