[FPSPACE] Fear and Loathing on the Launch Pad
dstdba at post4.tele.dk
Sat May 2 00:38:39 EDT 2009
From: E.P. Grondine [mailto:epgrondine at hotmail.com]
Sent: Saturday, May 2, 2009 03:21 AM
> The reason Baptistina type asteroids are rare
> is because they're captured dead comets and
> comet fragments.
Well, let's take a brief look at the orbit of
298 Baptistina. Its eccentricity is 0.096, its
perihelion and aphelion 2.047 AU and 2.481 AU
That makes for an asteroid with an orbit much closer
to circular than most asteroids, since according
to the Wikipedia experts Prussing and Conway: "Most
of the solar system's asteroids have eccentricities
between 0 and 0.35 with an average value of 0.17."
The eccentricities of comets lie in an entirely
different range. From the same Wikipedia article:
"The eccentricity of comets is most often close to 1.
Periodic comets have highly eccentric elliptical orbits,
with eccentricities just below 1; Halley's Comet's
elliptical orbit, for example, has a value of 0.967.
Non-periodic comets follow near-parabolic orbits and
thus have eccentricities very close to 1. Examples
include Comet Hale-Bopp with a value of 0.995086 and
Comet McNaught with a value of 1.000030."
Your favourite comet SW3 has an eccentricity of 0.6934
and corresponding perihelion and aphelion of 0.9391 AU
and 5.187 AU respectively. That makes it a full-blown
Arguing as you are, Ed, that 298 Baptistina with
a near-circular orbit is a "captured dead comet"
comes across, frankly speaking, like a load of bull!
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