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question: How far out can a planet be if it has a roughly circular orbit? At some point outwards neighboring heavy things will make it unstable.

UnlockedSecrets 5y ago
The oort cloud that is theorized to exist is hypothesized to be up to several lightyears out. https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud
- OneEyedRobot 5y ago
  It seems to me that something that's a couple of lightyears out can't have any sort of stable orbit. I suppose that an Oort cloud essentially merges with an adjacent star's so there's no hard definition.
  - lumost 5y ago
    At the point of merger with neighboring stars it’s likely that circular orbits are unstable. Judging by our own solar system it’s likely that the distance at which circular orbits are stable is a question of relative mass, and time.
  - nkrisc 5y ago
    > there's no hard definition. Yes. All human definitions are imperfect.
- vmception 5y ago
  Do other systems have oort clouds or are their’s also something we cant see from this far
  - UnlockedSecrets 5y ago
    The only physical evidence we have they exist are comets that occasionally show up in the inner solar system where we could observe them which have orbits that are not interstellar but would put them as going incredibly far out. From that we can extrapolate that they likely exist around every star but there is no way we could verify that with our current technology since any light reflected off the objects would be far too faint to detect.
- dehrmann 5y ago
  > https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud The distances between the planets fit nicely on a log scale.
Asraelite 5y ago
This limit is called the Hill Sphere: https://en.wikipedia.org/wiki/Hill_sphere https://en.wikipedia.org/wiki/Hill_sphere For the Sun it's a bit more than 1 light year, but in practice almost all orbits will be quite a bit under this: less than 0.8 ly.
- koheripbal 5y ago
  The Hill Sphere also changes over time as stars pass us. The galaxy is more of a soup - the stars in the neighborhood don't have a static position to one another. ...so I would imagine that anything even 1ly out would be unstable, over several hundred million years. Solar systems may even exchange very outer outer "planets".

UnlockedSecrets 5y ago

The oort cloud that is theorized to exist is hypothesized to be up to several lightyears out. https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud

OneEyedRobot 5y ago
It seems to me that something that's a couple of lightyears out can't have any sort of stable orbit. I suppose that an Oort cloud essentially merges with an adjacent star's so there's no hard definition.
- lumost 5y ago
  At the point of merger with neighboring stars it’s likely that circular orbits are unstable. Judging by our own solar system it’s likely that the distance at which circular orbits are stable is a question of relative mass, and time.
- nkrisc 5y ago
  > there's no hard definition. Yes. All human definitions are imperfect.
vmception 5y ago
Do other systems have oort clouds or are their’s also something we cant see from this far
- UnlockedSecrets 5y ago
  The only physical evidence we have they exist are comets that occasionally show up in the inner solar system where we could observe them which have orbits that are not interstellar but would put them as going incredibly far out. From that we can extrapolate that they likely exist around every star but there is no way we could verify that with our current technology since any light reflected off the objects would be far too faint to detect.
dehrmann 5y ago
> https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud The distances between the planets fit nicely on a log scale.

Asraelite 5y ago

This limit is called the Hill Sphere: https://en.wikipedia.org/wiki/Hill_sphere https://en.wikipedia.org/wiki/Hill_sphere For the Sun it's a bit more than 1 light year, but in practice almost all orbits will be quite a bit under this: less than 0.8 ly.

koheripbal 5y ago
The Hill Sphere also changes over time as stars pass us. The galaxy is more of a soup - the stars in the neighborhood don't have a static position to one another. ...so I would imagine that anything even 1ly out would be unstable, over several hundred million years. Solar systems may even exchange very outer outer "planets".