[meteorite-list] Study Suggests Giant Planet Ejected From Our Solar System

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 11 Nov 2011 14:55:10 -0800 (PST)
Message-ID: <201111112255.pABMtA0P027517_at_zagami.jpl.nasa.gov>

http://swri.org/9what/releases/2011/giant-planet.htm

Giant planet ejected from the solar system

For immediate release

Boulder, Colo. - Nov. 10, 2011 - Just as an expert chess player
sacrifices a piece to protect the queen, the solar system may have given
up a giant planet and spared the Earth, according to an article recently
published in The Astrophysical Journal Letters.

"We have all sorts of clues about the early evolution of the solar
system," says author Dr. David Nesvorny of the Southwest Research
Institute. "They come from the analysis of the trans-Neptunian
population of small bodies known as the Kuiper Belt, and from the lunar
cratering record."

These clues suggest that the orbits of giant planets were affected by a
dynamical instability when the solar system was only about 600 million
years old. As a result, the giant planets and smaller bodies scattered
away from each other.

Some small bodies moved into the Kuiper Belt and others traveled inward,
producing impacts on the terrestrial planets and the Moon. The giant
planets moved as well. Jupiter, for example, scattered most small bodies
outward and moved inward.

This scenario presents a problem, however. Slow changes in Jupiter's
orbit, such as the ones expected from interaction with small bodies,
would have conveyed too much momentum to the orbits of the terrestrial
planets, stirring up or disrupting the inner solar system and possibly
causing the Earth to collide with Mars or Venus.

"Colleagues suggested a clever way around this problem," says Nesvorny.
"They proposed that Jupiter's orbit quickly changed when Jupiter
scattered off of Uranus or Neptune during the dynamical instability in
the outer solar system." The "jumping-Jupiter" theory, as it is known,
is less harmful to the inner solar system, because the orbital coupling
between the terrestrial planets and Jupiter is weak if Jupiter jumps.

Nesvorny conducted thousands of computer simulations of the early solar
system to test the jumping-Jupiter theory. He found that, as hoped for,
Jupiter did in fact jump by scattering from Uranus or Neptune. When it
jumped, however, Uranus or Neptune was knocked out of the solar system.
"Something was clearly wrong," he says.

Motivated by these results, Nesvorny wondered whether the early solar
system could have had five giant planets instead of four. By running the
simulations with an additional giant planet with mass similar to that of
Uranus or Neptune, things suddenly fell in place. One planet was ejected
from the solar system by Jupiter, leaving four giant planets behind, and
Jupiter jumped, leaving the terrestrial planets undisturbed.

"The possibility that the solar system had more than four giant planets
initially, and ejected some, appears to be conceivable in view of the
recent discovery of a large number of free-floating planets in
interstellar space, indicating the planet ejection process could be a
common occurrence," says Nesvorny.

This research was funded by the National Lunar Science Institute and the
National Science Foundation. The paper, "Young Solar System's Fifth
Giant Planet?" by Dr. David Nesvorny was published online by The
Astrophysical Journal Letters.

Editors: An image and animation to accompany this release are
available at
http://swri.org/press/2011/giant-planet.htm


For more information, contact Maria Martinez (mmartinez at swri.org),
(210) 522-3305, Communications Department,
Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.
 
Received on Fri 11 Nov 2011 05:55:10 PM PST