Satgen 503 Comets and Meteors Pt2 by GM4IHJ (B(D SGEN503) 1998-11-14 Having established in recent years , that most meteors are debris released by Comets, it is reasonable to ask , where Comets come from. The Dutch Astronomer Jan Oort suggested that comets were resident far out from the Sun, well beyond the planets of the solar system, Residue left over from the formation of the planets, unable to form planets, these icy bodies are contained in a spherical cloud centred on the Sun, but nearly 1 million million miles from it, ie 1/24th of the way to the next nearest star. Far from the Sun and planets the majority of these small bodies have remained undisturbed for 4.5 billion years. Though at rare intervals, a passing star may come close enough , to send some of them far out into space to be lost from the solar system. Whilst other are slowed up by the stellar visitors gravity and lose orbit speed , falling slowly in towards the Sun. Recently , another Dutch astronomer ( G Kuiper) suggested that there was a closer, second comet reservoir, beyond the orbit of the planet Neptune, at a range of about 5000 million miles from the Sun. A fact confirmed in recent years, by the discovery of at least 60 small bodies, albeit big enough to be seen, in this Kuiper Belt. When disturbed these comets fall into an elliptical orbit coming much closer to the Sun at perihelion ( closest point to the Sun )but going back out to the Kuiper or Oort belt at aphelion. Unless, they come too close to one of the inner planet and are captured by say Uranus, which then confines them to an orbit going around the Sun at one end and Uranus at the other. As does the comet Temple-Tuttle generator of the November Leonids meteors. When inside Jupiters orbit , the heat from the Sun , melts some of the comets icy surface , releasing some of the trapped dust and fragments, which having, almost the same velocity as the comet, stream behind it , such that in a few hundred years there is a debris trail all around the comets orbit. Some comet orbits come near to, the orbit of the Earth around the Sun , and when they do, Earth runs into the debris stream. Twice in the case of a comet like Halley . Where the Earth meets the incoming and the outgoing stream. But only once in the case of most other meteor streams which intcept Earth orbit only once. So we get two showers a year from some comets, only one from others, and no showers at all from comets, which perhaps come in at very high inclination and miss Earths orbit track entirely. Recent studies to prove the above conjecture, have used examination of comet tracks to establish their perihelion distance fom the Sun and their orbital eccentricity ( easy for short period comets coming in from Jupiters orbit but much more difficult for the orbits with very high eccentricity where the comet comes fom the Oort cloud ). None the less, a detailed check of 190 of these long distance "presumed" Oort cloud wanderers has shown that their aphelion furthest from the Sun is roughly as expected ie around 1 million million miles or more. Do we ever get comets from other star systems ? Perhaps, once every 200 years, but only single stars like the Sun can be expected to retain comets. Binary star systems, probably cannot, hold on to comet clouds.