Originally posted by BZ
there was supposed to be a light show in the sky last night over the uk,from a comet(cant remeber its weird name!).
They're called the Perseids, and they're from remnants of Comet Swift-Tuttle.
it was cloudy and late so went to bed and didnt see anything
It was cloudy here as well. I was pretty bummed.
got me thinking anyway.
That's great! Not too many people seem to do that anymore!
how come comets seem to just go around space?is it just due to gravity from the planets pulling in a big orbit?
They do orbit the Sun, and yes it's because of gravity. The planets, especially the larger ones do have some effect on comets as well.
how far have comets been tracked to? if theyre flying around all the distance they do surely they pick up some space dust far out there.
We know comets mainly originate from the Kuiper Belt and Oort Cloud. The Kuiper Belt is generally recognized as the area from Neptune's orbit, 30 AU,
to about 50 AU and, for the most part, stays in the plane of the Solar System. The Oort Cloud is MUCH bigger; it extends out to about 3 ly away from
the Sun in a spherical pattern. This is where most comets come from. The way they get pushed into the Inner Solar System is usually by gravitational
forces from other stars or shockwaves from supernovae.
Keep in mind though, that the Oort cloud extends out 3 ly. The nearest star to our Sun, Proxima Centauri, is about 4 ly away. If it has an Oort clou
similar to our Sun's there is a slight possibility that some comets could be from another star system!
That is why there is all the ineterest in them, just as you said "surely they pick up some space dust far out there."
also if theyre made of ice, where did the ice come from,i know its cold up there but it was made somewhere,also i dont know much about space but,in a
gravity less and frictionless enviroment a small push on an object would see it carry on at that speed for infinity? what makes comets fly at these
high speeds,gravity or what pushed them in the first place?
Well we're not entirely sure how comets form, other than perhaps being leftovers of planets. Also, ice doesn't neccessarily mean water ice. Comets
are frozen gasses, normal hydrogen, oxygen, methane, carbon dioxide, and dozens of others. Yes, there is some water ice, but not all that much.
As I said above, what gets comets moving is usual gravitational interactment from a nearby star or from shockwaves caused by supernovae. Once a comet
gets moving towards the Sun, the Sun's gravity sucks it in more and more, causing it to speed up more and more.
Hope that that helps.
EDIT: Forgot to mention that 1 AU is equal to the average distance of the Earth and Sun. So 30 AU would be 30 times farther away from the Sun than the
[edit on 8/12/2005 by cmdrkeenkid]