sparks wrote: ↑Tue Sep 17, 2024 2:31 pm
"Later in the month, a smaller asteroid will become a temporary “mini moon” as it is pulled into orbit around Earth for two months."
Just wondering if that is an exact quote?
If so, it's at best poorly written. It deserves far more explanation as to how something that starts orbiting the Earth can, after two months suddenly de-orbit.
I wouldn't be able to repeat the mathematis today, but a few years ago I took an oline class from Coursera in spacecraft operations, that included orbital mechanics. Basically, there are eliptical orbits, and there are hyperbolic "orbits". I put the "orbits" in quotes, because they don't usually involve multiple revolutions around the planet/moon/object or whatever larger rock has captured them. An elliptical orbit is stable. Once it's there, it's there for good, barring interference from a third body. However, hyperbolic orbits are not. They go around the planet and then get flung into space again.
It's the same principle that's used when you hear about a "gravitational slingshot", where a space probe might travel to Venus and go around it to pick up speed so it can head out to Jupiter. It "goes into orbit" at Venus, but it's not a stable orbit. It flings it out toward Jupiter. They way it is usually described is a bit misleading, because it implies that the spacecraft picks up speed as it goes around Venus. It doesn't. However, its velocity changes, so that some of the kinetic energy that was carrying it around the sun at a certain speed, will now be sending it out into space. Of course this is all quite predictable so the folks at NASA or JPL or whoever figure out exactly where to approach Venus so that the spacecraft's orbit around the sun becomes a trajectory toward Jupiter or wherever the probe is aimed at.
In the case of the asteroid, it's just doing that naturally. It's being captured, but in a hyperbolic orbit that will fling it away naturally.
