Where do all the Comets go. . .?

Entering this thread late and I'm not going to pretend I read every word but the answer is gravitational pull of the greatest gravity lacking a greater gravity.

They originate in the Kuiper belt and Oort cloud where they orbit the sun at great distance in 'conventional' orbits. When disturbed by the gravitation of a relatively nearby star or other body, their orbits are disturbed and they 'fall' towards the sun.

You may be referring to something a bit different, I believe you may mean that object in the Kuiper belt that were not ever going to approach the inner solar system could be nudged by a passing large gravity body. The reality is there is nothing for several light years from the sun to overcome the gravity of the sun itself. So an object in or near the Kuiper belt orbits the sun because there is no greater gravity body close enough to overcome the gravity of the sun. Whether they ever come near the inner solar system or not is determined by the eccentricity of their orbit around the sun, how elliptical it is.

Orbital speed of a body around the sun slows the further away you get, (Mercury reaches near 110,000 mph, Earth about 66,600 mph, Jupiter about 29,000 mph, Neptune a crawling 12,000 mph) and so on. So one can understand how slowly an orbiting object around the sun can get 100x times the distance of Neptune. So that is how it takes tens of thousands of years for an object that far away from the sun to complete an orbit. Nothing of great mass is the proof that nothing else is out there to change this, that is why myths of 'Planet X's' are fantasy.

We have the capability to detect that.

Hi Illustronic,

I'm not a believer in a doomsday planet either. I was refering to this...

According to Oort, the comet cloud is relatively stable, except when the gravitational attraction of some passing celestial body (star, asteroid, another comet, etc.) disturbed the cloud, then a shower of comets would be shaken loose to be pulled towards the inner solar system by the Sun's gravitational influence.

Here's the link to the site...

All About Comets

reply to post by Insomniac


Yes comets are very small bodies, they don't necessarily mean passing huge dwarf stars are needed to nudge a tiny body to a collision to knock it into the inner solar system. It wouldn't take much out there to change trajectories or orbits due to the very lack of large gravitational bodies, which we can detect now.

Not criticizing what you posted, just trying to add some perspective to scale and distance.

We know of one tiny red dwarf 4 times the distance beyond our sun's Oort cloud and that is in just one direction and it is locked within its own star system. We can detect that so why couldn't we detect something 1/4 that mass 4 times closer? Not saying you said that. It was brought up by the OP and this is an illustration of scale.

So I was more using your post to shed light on the 'speculative theory' brought up by the OP, that there is no large mass body out there coming to get us, small bodies out there are pinballs, and largely wouldn't survive the trip to the inner solar system like comet Elenin.

reply to post by Illustronic


Absolutely. The presence of Tycho is hypothesised by astronomers John Matese and Daniel Whitmire and they make what sounds a convincing case to the layman. They propose that an object with four times the mass of Jupiter is orbiting within the Oort cloud. But as they've received no support from the scientific community it would seem that they're probably wrong, however they hope that WISE will detect it... I'm not holding my breath.

Originally posted by Illustronic
We know of one tiny red dwarf 4 times the distance beyond our sun's Oort cloud and that is in just one direction and it is locked within its own star system. We can detect that so why couldn't we detect something 1/4 that mass 4 times closer? Not saying you said that. It was brought up by the OP and this is an illustration of scale.

So I was more using your post to shed light on the 'speculative theory' brought up by the OP, that there is no large mass body out there coming to get us, small bodies out there are pinballs, and largely wouldn't survive the trip to the inner solar system like comet Elenin.

I appreciate your input and it is enlightening. That kind of information is exactly why I'd posted the thread. I was hoping that someone far more learned than I on these matters could show how this aspect of our Galaxy works, since it seems more than a bit confusing. This certainly explains something like Sedna though. I'm still a little fuzzy on how the Sun is still exerting enough pull at over a light year away to draw something like Comet West back in the direction it had come from...and take 250,000 to over a Million years to do it..but mysteries are what fuel the imagination and we have to have a few left out there, right?

BTW...I know I spend a lot of time on the Doomey forums, but I do try not to carry that corner of ATS and thinking into every other forum I've got personal interest in the topic of...as I'd noted earlier, I really had no intention of bringing any of the doomer topics into this question, in even a passing way. It's why I used Tyche graphics, not Nirbiru. One is theorized to throw things at us and the other is said to throw ITSELF at us.

Thanks again for the solid factual input though. It's what makes the time to write a thread worth it.

reply to post by Wrabbit2000


They get hijacked by Terrorists, they use it against their family's.

Watch out man!

Some comets just aimlessly wander throughout whatever galaxy they happen to be in until their trajectory is disturbed and altered by the gravity of another object,or when they collide with something and some short period comets originated from within the kuiper belt and some from the oort cloud thats one light year away from us and contains billions of comets! But do comets and comets that have burned off all their outer layers to become asteroids,ever leave a galaxy? Oort Cloud > en.wikipedia.org... Kuiper Belt > en.wikipedia.org...

reply to post by blocula


It's a lovely thought... Intergalactic asteroids on a lonely journey through deep space. Sadly I don't think it could happen though as they would be bound by the gravity of the galaxy.

reply to post by Wrabbit2000

I appreciate what you're saying and it does make sense to a great many of the objects. However, it doesn't seem to make much logical sense to the very long ones.

But why should separate laws of motion apply to long-period comets? Gravity and inertia apply to all bodies in the same way. Explain your doubts regarding this point and I will try to resolve them.

I'm truly curious and open to understanding...I'm not posting to carry any agenda at all.

That's good. I've already given you the correct answer. So did Chadwickus and nineix, who posted at about the same time as I. Illustronic and Insomniac are on the same page too.

The motion of comets is based on laws of motion and gravity that have been well understood since the eighteenth century. These laws are regularly used both to track and to predict accurately the paths of comets, asteroids, planets and other astronomical bodies. They are also used to calculate the speeds and trajectories of the spacecraft we despatch to destinations all over the Solar System. The laws, to state the obvious, work; they have been proven to do so times without number, and they completely explain the trajectories of all bodies in space, long-period comets included.

Just to repeat myself: if there were another body involved in a Sun-comet interaction it would change the shape of the comet's orbit completely and make the prediction of periodic comets much more difficult – in some cases, no doubt, all but impossible.

To forestall nitpickers, I will add that, in fact, all bodies in the Solar System affect one another gravitationally, but in most cases the primary-secondary interaction far outweighs the consequences of any third-body interaction. The exceptions are things like the moons of Jupiter, which are the subject of a constant gravitational tug-of-war between their primary and the Sun, besides interacting gravitationally with one another.

reply to post by Astyanax

I'm about brain fried for the day and heading for sleep. If you might indulge me a bit more to check back later tomorrow, I will put a bit of time and thought into how I present the question still nagging at me... It sounds like if I can form my thoughts into words well enough, you'll probably have a very direct answer and that would be appreciated.

Thanks for your reply and the others...It's great to have gotten serious response and for that reason I do want to take more than 5 minutes and a bunch of words in forming a solid point to clarify.

reply to post by Astyanax

Well, what a difference a day's sleep can make. I'm a bit humbled to find that in spending a fair part of the evening tonight looking into this (getting lost in the subject might be more accurate..lol) It seems the problem hasn't been in how I asked the question but in the scale I was thinking on at all. The sheer size of anything beyond our inner planets is just so mind boggling.

I'd seen many graphics and illustrations along side articles saying the Oort cloud which seems to orbit our Sun in an enormous sphere ( ? ) of debris and comet material was 50,000 A.U. and few that took that the next step to show it then EXTENDED another 50,000 AU across.

In short, the great information from several here and the directions that sent me off in, more than answered my question and just opened a new set of them for how our Sun has influence that far out, yet still gives habitable conditions this close to it. Oh well...That is something for another thread though.

Thank You everyone for the input and when someone asks for an example of where a thread helped inform, well, here is one of them. If I go past Associates level for school, I may just see about a class as an elective somewhere along the way for this.... The whole topic is just endlessly fascinating.

reply to post by Wrabbit2000

Really enjoyed your thread - visually and content-wise. (Pun intended.) Also enjoyed the content that Mianeye added. Mike Brown, discoverer of Sedna, kept an online diary of sorts wherein he speculated on what could possibly cause an orbit like that.

There is something out there

If you get kicked by Neptune, you can go zooming off into the unchartered regions far beyond the Kuiper belt, but you will come back to see Neptune again.

The exception to this rule is, of course, Sedna. Sedna has one of the most elongated orbits around, but it never comes anywhere close to Neptune or to any other planet. Indeed, the earth comes closer to Neptune than Sedna ever does.

The orbit of every single other object in the entire solar system can be explained, at least in principle, by some interaction with the known planets (and, again, for you Oort cloud sticklers out there, the known galactic environment). Sedna alone requires Something Else Out There.

Either something large once passed through the outer parts of our solar system and is now long gone, or something large still lurks in a distant corner out there and we haven’t found it yet.

The second possibility that we considered and wrote about was that perhaps a star had passed extremely close to our solar system at some point during the lifetime of the sun.

Looking at the number of star near us in the galaxy and fast they all move relative to each other, we found that the chances of such a rogue star encounter happening sometime in the past 4.5 billion years was around 1%.

When we found Sedna, we, too, knew what was next: head back out into the night and keep looking. Until we found more, we wouldn’t know what this profound bit of the solar system was trying to scream so loudly in our ears.

The ancient passing star explanation is the one I quoted although the odds for that one are not good. However, whether the odds are not good because it's impossible to recreate that or because of other reasons is not clear.

The other two possible reasons he gives are an object way out there as yet undiscovered and also multiple close encounters from multiple stars in ancient times.

The Oort cloud comets are interesting because they are the ones that set Matese and Whitmire on a search for Tyche as an explanation for what propelled them.

Can WISE Find the Hypothetical Tyche

NASA-WISE-Tyche

The full survey, scheduled for release in March 2012, should provide greater insight. Once the WISE data are fully processed, released and analyzed, the Tyche hypothesis that Matese and Whitmire propose will be tested.

reply to post by luxordelphi

Good post. A star for you.

However, whether the odds are not good because it's impossible to recreate that or because of other reasons is not clear.

The odds are not good because space is very big, that's all.

But space is also so big that things with the odds well against them happen all the time.

Sedna may be the Death Star for all we know.

reply to post by Wrabbit2000
I really like how most threads that people make here at ATS not only expose and discuss the issue at hand,but they also reveal other ideas,other theories and other mysteries throughout the numerous follow up replies that so many intelligent people take the time to post,its endlessly fascinating for me...