That's the way the comet crumbles: Hubble image shows remains of Comet ATLAS

Mar 19, 2020
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Where is the carbon monoxide data?! Did they see a burst of CO when this thing broke up? Data to follow hopefully.

And how do they know it originated in a hypothetical Oort Cloud when it could have come from the more likely existing Hills Cloud, or even the scattered disc? And please don't suggest its orbital characteritics as proof of origin, since it is not!

This answer should be obvious. They can't know!
 
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Dec 23, 2019
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And how do they know it originated in a hypothetical Oort Cloud when it could have come from the more likely existing Hills Cloud, or even the scattered disc? And please don't suggest its orbital characteritics as proof of origin, since it is not!

This answer should be obvious. They can't know!
If you don't want to talk about the orbital mechanics then you don't really want to talk about origins. Those are determned by orbital mechanics. Everything you said with that is just flute music.
 

Catastrophe

The devil is in the detail
Feb 18, 2020
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Just today I gave been reading about all these telescopes and what they are going to achieve and what theories they will substantiate. Dark energy - dark matter - and the leftovers (that means us).
I am amazed and flabbergasted. Probably the most amazing was to see the remnants of Comet Shoemaker-Levy 9 hitting Jupiter.
It just confirmed for me the possibilities and probabilities of the other impacts - Theia hitting pre-Earth; Venus and Uranus; and the rest.
 
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Orbital mechanics are great for well established objects like planets and moons. The origin of many comets is actually unknown. Hypothetical clouds of comets are not proofs, they are postulates.

Orbital mechanics can only suggest their origins, and cannot offer unequivocal proof. It is clearly biased from one source or another. I am rather fond of the unequivocal vs. models. Gravitational interactions over eons with gas giants, the sun, and asymmetric out-gassing cannot be modeled to provide origins of such objects.
 
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Just to add to my last post:

Voyager I's trajectory was directed (gravity-assisted) off the ecliptic by ca. 35 degrees to the north during its designed close encounter with Saturn* (NASA - right, what do they know?). If it were to return covered in ice, it surely would not have an orbit along the ecliptic, and some would consider it an icy comet from some distant cloud of comets which must have persisted for billions of years. How else could it have such an orbit?

It should not be difficult to appreciate that the gravitational impact of inner solar system objects could dramatically alter a comet's orbital motion, suggesting it came from any direction in the sky. Even more so when you consider this activity has been happening every time it enters the solar system - for many comets, hundreds of times or more. Indeed, it would be very surprising if its orbit remained unchanged after a few passes, to say nothing of so many it could have made.

Clearly any accurate modeling of the origin of comets from orbital mechanics needs to look at gravitational effects from larger bodies in the inner solar system (for a great example of this issue, see NASA re: "sling-shotting"), and what it means about trajectories. Voyager 1 proves that this is non-trivial in the extreme. I suspect that such models could not possibly take these events into account. The origin of many comets remains a mystery until unequivocal proof is established. That is not currently the case.

Incidentally, Halley's comet is fairly well established. Remarkably, it is believed to have been in a much larger orbit, and then because of inner gravitational forces, its orbit was greatly modified and now reaches out to around the orbit of Pluto. Modeling the origin of comets is clearly not an easy task. And every comet will be different, potentially to some degree(s), and in more ways than one.

There are good reasons I don't want to hear about orbital mechanics and comet modeling, zclayton. If you have anything brief to add that punches any holes in my commentary, I would be happy to entertain them. Try not to drag too many details about comet orbits in. After reading about Halley's Comet recently, I just don't see mechanics as an issue to debate. My apologies for having been there, done that too many times. You caught me on a bad day.

Now out-gassing of various things are of great interest to me after the 2I/Borisov data. That showed a big spike in CO emissions. If you have knowledge of this for various comets, that would be something I know little of and could indicate where they formed in the early stages, depending on emissions. But there are also other factors in out-gassing content you might know if you have studied it.


* https://voyager.jpl.nasa.gov/mission/interstellar-mission/
 
Apr 27, 2020
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What you described regarding Voyager is orbital mechanics. So, what’s the issue here, or you perhaps think that only trajectories of planets abide that law? Slingshot effect is the result of smart application of orbital mechanics law. Consequently, comets also abide that law. And yes, they interact with other celestial objects and most particularly with sun who rules entire system.
Just to add to my last post:

Voyager I's trajectory was directed (gravity-assisted) off the ecliptic by ca. 35 degrees to the north during its designed close encounter with Saturn* (NASA - right, what do they know?). If it were to return covered in ice, it surely would not have an orbit along the ecliptic, and some would consider it an icy comet from some distant cloud of comets which must have persisted for billions of years. How else could it have such an orbit?

It should not be difficult to appreciate that the gravitational impact of inner solar system objects could dramatically alter a comet's orbital motion, suggesting it came from any direction in the sky. Even more so when you consider this activity has been happening every time it enters the solar system - for many comets, hundreds of times or more. Indeed, it would be very surprising if its orbit remained unchanged after a few passes, to say nothing of so many it could have made.

Clearly any accurate modeling of the origin of comets from orbital mechanics needs to look at gravitational effects from larger bodies in the inner solar system (for a great example of this issue, see NASA re: "sling-shotting"), and what it means about trajectories. Voyager 1 proves that this is non-trivial in the extreme. I suspect that such models could not possibly take these events into account. The origin of many comets remains a mystery until unequivocal proof is established. That is not currently the case.

Incidentally, Halley's comet is fairly well established. Remarkably, it is believed to have been in a much larger orbit, and then because of inner gravitational forces, its orbit was greatly modified and now reaches out to around the orbit of Pluto. Modeling the origin of comets is clearly not an easy task. And every comet will be different, potentially to some degree(s), and in more ways than one.

There are good reasons I don't want to hear about orbital mechanics and comet modeling, zclayton. If you have anything brief to add that punches any holes in my commentary, I would be happy to entertain them. Try not to drag too many details about comet orbits in. After reading about Halley's Comet recently, I just don't see mechanics as an issue to debate. My apologies for having been there, done that too many times. You caught me on a bad day.

Now out-gassing of various things are of great interest to me after the 2I/Borisov data. That showed a big spike in CO emissions. If you have knowledge of this for various comets, that would be something I know little of and could indicate where they formed in the early stages, depending on emissions. But there are also other factors in out-gassing content you might know if you have studied it.


* https://voyager.jpl.nasa.gov/mission/interstellar-mission/
 
Mar 19, 2020
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Haley's comet says it all.

Presumed to have arisen from some distant source, now in ca. 76 year orbit due to gravitational interactions after multiple passes through solar system. The reverse process can clearly result in long period comets arising from a local source.

Orbital mechanics are good for short term predictions but simply cannot tell a comet's origin. Many Haley's type comets have inclinations extending from zero to more than 90 degrees. And that just for Haley's class of comets.

No one with knowledge of the effects of time and gravitational interactions on such objects would rationally offer a validated means by which to predict origins.

If orbital mechanics is all you have, we are done.
 

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