Why are most planetary orbits nearly circular?

Does the gravitational attraction of the Milky Way really increase the eccentricity of planetary orbits in the Kuiper Belt over time?

• I attended someone's AGU poster today, whose paper is here: http://www.rochesterresearch.org/wp-content/uploads/2010/09/planetary_orbits_man_mass_web_pdf_2_11_07.pdf I don't have the time to go over the calculations now (AGU Meeting), but I just would like to know what others think of this... TITLE: Eccentricity Increase of Planetary Orbits in the Kuiper Belt with Distance and Time ABSTRACT BODY: Beyond Neptune the eccentricity of orbital objects significantly increases with distance (2009 AGU Fall Meeting). The eccentricity eventually reaches the critical value of 1.0 at about 300AU (4.6E+10 Km), where elliptic orbits will change to hyperbolas. This observation predicts that planets leave the Solar system when they reach the limiting distance. In this presentation, this observation is quantitatively modeled and a physical explanation for the increase of eccentricity with increasing planetary orbits is suggested. The model is based on the interaction of the gravitational fields of the Sun and the Milky Way galaxy. Previously a quantitative model was presented for the rate of the decrease of the solar gravitational field with time. This loss is caused by solar mass and gravity loss by radiation and solar wind. With time the solar gravitational field decreases relative to the gravitational attraction of planets by the Milky Way. It is shown that the increasing power of the galactic gravitation is expanding planetary orbits near the galaxy, which eventually breaks the adhesion of the planets from the solar system. On the opposite side of the Sun, the gravitational forces of the Sun and the galaxy combine to enhance the planetary adhesion. The result is an increase of ellipticity of planetary orbits which increases with distance from the Sun. The experimental and model results preclude the existence of an Oort cloud beyond the limiting escape distance.

• Answer:

  OK.  The first part of the paper was sort of interesting when he was talking about how stellar mass loss affects planetary orbits.  There might be something interesting there for studying how exo-planet systems evolve over time. When it tries to relate all of this to the expansion of the universe and the Hubble Constant, the paper falls off the rails.  The phenonomeon of stellar mass loss as nothing to do with the cosmic expansion.  When a star loses mass, the mass stays within the galaxy so it doesn't affect how the galaxy interacts with other galaxies.  Also Hubble expansion just doesn't happen within galaxies.  One analogy is that gas is made up of atoms but you can pretend that a gas is smooth.  The universe is made up of gas/dust and galaxies but you can pretend that the universe is smooth.  When you look at individual atoms, the "smooth picture" breaks down and likewise when you look at individual galaxies the "smooth picture" breaks down. With some more editing and some more citations, the first part might be publishable, but when he brings in the cosmology, it's clear that he doesn't understand cosmology in that section, and the last part of the paper pulls down the first part. Also the paper doesn't mention competition with the MW.  The order of magntitude doesn't seem to work, and since the author put cosmology stuff in this paper that is clearly wrong, his model of gravity fields in the MW is highly suspect. I'm personally rather nice, but there are people that would rip the paper to shreds.