Satgen 606  Kuiper Belt Objects by GM4IHJ  (BID SGEN606)  2000-11-04

There has been controversy with respect to Pluto, the outer most
planet of our solar system, ever since its discovery by Clive
Tombaugh in 1930. It is small, and appears to have survived its close
association with the outer most giant planet Neptune, only because of
its orbital resonance with Neptune. Whereby, Neptunes 165 year orbit
period is exactly 2/3 of the orbit period of Pluto. Which despite the
fact that Pluto moves inside Neptunes orbit at times, ensures they do
not collide.

At first sight this appears to have been a lucky chance. But it is no
coincidence. Had it been otherwise Pluto would have been pushed into
the inner solar system long ago, or, pushed out to the stars never to
return. However over the past 10 years this picture of unique lonely
Pluto has been blown apart by the discovery of more than 300 faint
objects out beyond Pluto between 30 and 50 Astronomical units (AU),
from the Sun (where 1 AU = 93 million miles).

Just after Pluto's discovery , Leonard was suggesting the possibility
of lots of small bodies slightly further out. Then in 1950 Kuiper
suggested that this part of the solar system was where most of the
short period comets came from. But only in the last decade have
bigger and better telescopes revealed their presence. Kuiper and
others thought this was where comets were borne at the same time as
the planets were formed. But the big gas planets forced many of then
out to 20,000 AUs from the Sun into what is called the Oort belt. A
belt proposed by the Dutch astronomer Jan Oort to account for the
apparent aphelion points furthest from the Sun where the long ( as
opposed to Kuiper belt short ) period comets came from.

The Oort belt is presently too far out to see, but not so the Kuiper
belt where recent studies suggest several different types of small
bodies are present. Referred to as KBOs, some of these objects seem
to mimic Plutos orbital resonances with Neptune, hence their name
Plutinos. But much more numerous are a group referred to as the
classic KBOs which are further out with mean distances from the Sun of
about 44 AUs. While in much more highly elliptical orbits there is a
class of objects catalogued as, scattered disk objects.

Scattered disk objects are widely dispersed throughout the outer
solar system, possibly as a consequence of having been perturbed and
thereby escaped from the Kuiper belt , and in consequence , much more
likely than the stable orbit KBOs, to eventually wander into the
inner solar system and be forced into a short period orbit by a close
encounter with Jupiter or Saturn. Remaining thereafter trapped in a
short, less than 150 year cometary orbit , gradually losing more and
more material with each perihelion passage around the Sun.

Eventualy astronomers will find a way to more closely catalogue the
KBOs and their kin, and even hint at which ones may be the next to
drop in towards the Sun, and reveal themselves as Comets. Meanwhile
,thinking back in time, perhaps those Leonids we will hopefully see
and hear on 17/18th November next , were once, millions of years ago,
part of an icy KBO.