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D. F. Bartlett (University of Colorado)
At recent meetings of the AAS I have presented posters defending a new, sinusoidal gravitational potential. Here the customary numerator in Newton’s law is replaced by GM cos(2\pi r/\lambdao) where \lambdao is a universal constant, 425 pc. Because there are 20 oscillations of the potential between the sun and the center of the Milky Way, galactic tidal forces should be about 120 times as strong as normally believed.
Such a large tidal force is needed if the global galactic potential is to explain the surprisingly large modulation in the galactic longitude of the perihelia of comets teased from the Oort cloud. (A modulation with prominent peaks at longitudes of 45,135,… degrees was first observed by Matese and Whitmire (1996). They now feel that an impactor is the culprit, but it could instead be the sinusoidal potential (Bartlett, AAS-199)).
Here I discuss how the same large tidal force might be responsible for two more observations in our solar system. Recently, Shaviv and Veizer (2003) have found a periodicity of about 140 Myrs in the observed isotopic fraction of heavy oxygen (O-18) in terrestrial calcite. They ascribe the period to variations in the cosmic ray rate caused by the revolution of the solar system through 4 rotating spiral arms. I find it rather to be the effect of variations in the strength of the galactic tidal force as the sun rotates in the nearly stationary quadrupole field of the central bar.
There is increasing evidence that the Kuiper belt really ends at about 50 AU. (Donnes 1997; Allen, Bernstein, and Molhotra 2001). The cause for this cut-off is unknown, but galactic tidal forces are dismissed. I will show how the new, stronger forces can be effective.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.