by Chris Peterson » Thu Apr 18, 2024 3:46 pm
johnnydeep wrote: ↑Thu Apr 18, 2024 3:23 pm
Chris Peterson wrote: ↑Thu Apr 18, 2024 2:16 pm
shaileshs wrote: ↑Thu Apr 18, 2024 3:59 am
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.
[quote=johnnydeep post_id=338421 time=1713453790 user_id=132061]
[quote="Chris Peterson" post_id=338420 time=1713449780 user_id=117706]
[quote=shaileshs post_id=338412 time=1713412780 user_id=143908]
I wonder what makes the comet get too close to the Sun ? I'd imagine gravity pull .. but then, how long it must have taken that comet to reach that stage (i mean how many times it must have made rounds around Sun and how many years it must have been doing it before finally getting too close and getting disintegrated) ? And, will the same thing happen to planets in our solar system too (will they get closer and closer over hundreds of millions of years and eventually get disintegrated OR before that happened Sun will reach 10B and will begin end of life phase by expanding and gulping planets till Mars) ?
[/quote]
To add to Ann's explanation of gravitational perturbations: it does not need to take a long time. A comet may go around for thousands of years and never get close to the Sun, and then pass too near Jupiter and be deflected so it hits it (not common, but very much possible).
Orbital systems with just two bodies are stable. Their orbits will never change. But if you have three or more bodies, that stability is lost. Such systems will always change over time. Wait long enough and all the planets in the Solar System will be flung into interstellar space or into the Sun (except probably for Jupiter, which in the end would become a two-body system with the Sun). In theory even a two-body system will decay if you give it long enough, since bodies in orbit radiate gravitational radiation (like we pick up from merging black hole systems). But that energy loss is incredibly small, so the time scales are huge.
With comets, a few other things are going on. First, they are small and have non-uniform surfaces and shapes. So as they orbit, they are subject to forces from photons and even solar wind. That can slightly tweak their orbits. Second, as they near the Sun and expel gas and dust, their mass changes and they experience reaction forces. This also changes their orbit slightly. All of these effects are tiny, but they make it very difficult to accurately predict where a comet is going to be in hundreds or thousands of years, as these small effects, along with gravitational perturbations from Jupiter and Saturn, accumulate.
[/quote]
But I suppose even if there are only two bodies in a system, like, say, the Sun and Jupiter, the Sun may - and will - change mass over time through its evolution along the Hertzsprung-Russell diagram due to changes in its nuclear fusion processes. So I'd think that could also eventually perturb Jupiter's orbit?
[/quote]
Yeah, because a true two-body system consists of point masses. In the real world, the two bodies aren't points or perfect, homogeneous spheres. So there are other forces involved (like tidal ones), and as you note, masses can change due to lost material. In practice, though, I don't think the changes the Sun or Jupiter will go through would ever result in Jupiter being ejected. Just having its orbital parameters tweaked.