NASA predicts asteroid to make one of closest approaches to Earth ever recorded

Re:NASA predicts asteroid to make one of closest approaches ... by graderjs on Thursday January 26, 2023 @09:47AM (#34532225)

I wish they publicised error bars on these approach distances.

What's the equation to calculate if such object given its mass, velocity, etc would get pulled into Earth orbit or collision or just fly past?

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Re:NASA predicts asteroid to make one of closest approaches ... by lamacase on Thursday January 26, 2023 @01:23PM (#34536183)

The equation is: if it isn't already in orbit, and it doesn't hit the atmosphere, then it flies past.

For an incoming object to start orbiting earth, it has to decelerate through active propulsion or aerobraking or something like that.

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Re:NASA predicts asteroid to make one of closest approaches ... by graderjs on Thursday January 26, 2023 @09:44PM (#34541837)

Sounds like a nice heuristic but I don’t think that covers every case—and it’s not an equation. Sorry, wrong answer!!

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Re:NASA predicts asteroid to make one of closest approaches ... by lamacase on Friday January 27, 2023 @09:47AM (#34546613)

It does cover every case though. The solution for the orbit of a mass in a 2-body problem is always an ellipse! (Or a parabola/hyperbola for an escape trajectory). You can find the derivation here [1], it's not too complicated.

There is no way for an asteroid and the earth to interact gravitationally to change the asteroid's orbit from what it was coming in. Non-gravitational interactions (like hitting the earth/atmosphere) can do it.

Also, over many interactions and a long time you can have orbital capture in many-body situations, but there is no general equation for this (look up 3 body problem). This is how you get objects accumulating at Lagrange points for example.

TLDR: The equation you're asking for does not exist. Sorry, wrong question!!

https://en.m.wikipedia.org/wiki/Orbit

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