fisher@ocala.DEC (Burns Fisher ZKO1-1/D42 DTN 381-1466) (01/13/86)
I read this weekend (Boston Globe?; possibly Space World) about a new theory of the formation of planets which is sufficiently precise to allow the prediction of planetary locations as well as those of their satellites. The article said that the theorist, an Australian, had made a number of predictions about Uranus based on the theory. The first of these, a prediction of the existance and location of a previously unknown Uranian satellite, has been confirmed by Voyager II. Several others will be confirmed or denied over the next few weeks. The article says that if this theory holds up it will be a great shock to the scientific community. Does anyone know anything about this? Is it for real? The article says that the theory agrees with the current known planetary system. But what does the theory have to say about the asteroid belt, Deimos/Phobos, Pluto, and trans-Plutonian planets? Thanks for any info. Burns ...decwrl!rhea!star!fisher
snell@utzoo.UUCP (Richard Snell) (01/15/86)
A front page article in a U of Toronto newspaper "The Newspaper"
refers to the "shepard theory" of Prof. Scott Tremaine (Canadian Institute
of Theoretical Astrophysics), Prof. Peter Goldreich (California
Inst. Technology), and Dr. Nicole Borderies (Pic-du-Midi Observatory,
France). Portions of this article are reproduced:
"Uranus is known to have five satellites surrounding it. The scientists
believe that 10 additional satellites are the only plausible theory
to explain why the rings of Uranus are so narrow. In theory, the
constant jostling of one ring particle against another should have
spread any narrow ring-like structure into a much broader diameter.
Despite the fact that Uranus's rings are some 300,000 kilometres in
circumference, the width of the rings themselves is only 2-3 kilometres.
"[They] suggest that if each ring was accompanied by small satellites
or moons - on inside and one outside - the gravitational forces of
these moons could overcome the natural tendency of a ring to spread...
""The satellites act somewhat like shepards keeping a flock of unruly
sheep in order and hence are called `shepard' satellites... It is difficult
to understand without shepard satellites how such perfectly sharp
and well-defined structures (ringsystem) could be maintained over
the age of the solar system," [Tremaine] added.
"In response to a question of what a sucessful prediction whould (sic)
mean to the discipline, Tremaine responded, "It certainly won't
revolutionaize my thinking... but one broad implication
for the study of planetart rings is it gives you clues as to how the
system (of disks and planets) works that can be applied to other systems
of galaxies and solar systems."
"... when the Voyager 2 mission went past Saturn, it discovered a
previously unknown ring that shares characteristics with the Uranus
structure. The Saturn ring was narrow and accompanied by two shepard
satellites on either side of it
--
Name: Richard Snell
Mail: Dept. Zoology, Univ. Toronto
Toronto, Ontario, Canada M5S 1A1
UUCP: {allegra,ihnp4,linus,decvax}!utzoo!snell