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Detecting the objects is the hard part. The planet killers are all likely to be highly elliptical objects with large orbital periods (on the order of thousands

by knappe 3y ago

Detecting the objects is the hard part. The planet killers are all likely to be highly elliptical objects with large orbital periods (on the order of thousands of years). With that kind of orbital period, we'd be lucky to see it before it has impacted.

AnimalMuppet 3y ago
> The planet killers are all likely to be highly elliptical objects with large orbital periods (on the order of thousands of years). Not saying you're wrong, but... what is your basis for claiming that this is true?
- Thiez 3y ago
  Planets, by definition, have cleared their orbits around their respective star. So a planet killer threatening earth cannot share the earths orbit, or earth wouldn't be a planet. So a circular orbit shared with the earth is ruled out. But if it had a circular orbit that did not intersect the earths orbit, then there would be no chance of it hitting earth, so not really a planet killer either. The possible orbits that remain must be elliptical. Now if a planet killer passed us every year then we probably would have hit them by now (or provided a gravity slingshot to alter its orbit!), so it follows that it must have a large orbital period :p
- knappe 3y ago
  The snarky answer would be to just leave this link https://en.m.wikipedia.org/wiki/Orbital_mechanics https://en.m.wikipedia.org/wiki/Orbital_mechanics. But to more fully answer the question look to https://en.m.wikipedia.org/wiki/Elliptic_orbit https://en.m.wikipedia.org/wiki/Elliptic_orbit Notice that the object with an eccentricity of 0.8 has a much faster speed as it approaches the mass it is orbiting. So, to extrapolate, objects with a high eccentricity will be moving much faster as their semi major axis decreases (as they get closer to the mass it is orbiting). Faster means less time to detect the object. Less time to detect the object means we have less time to react to the object. Less time means planet killer. And keep in mind the time periods we're talking about for some of these objects measure in the tens of thousands of years. So we don't really get a chance to record these objects for "next time".

by knappe 3y ago

AnimalMuppet 3y ago

> The planet killers are all likely to be highly elliptical objects with large orbital periods (on the order of thousands of years). Not saying you're wrong, but... what is your basis for claiming that this is true?

Thiez 3y ago
Planets, by definition, have cleared their orbits around their respective star. So a planet killer threatening earth cannot share the earths orbit, or earth wouldn't be a planet. So a circular orbit shared with the earth is ruled out. But if it had a circular orbit that did not intersect the earths orbit, then there would be no chance of it hitting earth, so not really a planet killer either. The possible orbits that remain must be elliptical. Now if a planet killer passed us every year then we probably would have hit them by now (or provided a gravity slingshot to alter its orbit!), so it follows that it must have a large orbital period :p
knappe 3y ago
The snarky answer would be to just leave this link https://en.m.wikipedia.org/wiki/Orbital_mechanics https://en.m.wikipedia.org/wiki/Orbital_mechanics. But to more fully answer the question look to https://en.m.wikipedia.org/wiki/Elliptic_orbit https://en.m.wikipedia.org/wiki/Elliptic_orbit Notice that the object with an eccentricity of 0.8 has a much faster speed as it approaches the mass it is orbiting. So, to extrapolate, objects with a high eccentricity will be moving much faster as their semi major axis decreases (as they get closer to the mass it is orbiting). Faster means less time to detect the object. Less time to detect the object means we have less time to react to the object. Less time means planet killer. And keep in mind the time periods we're talking about for some of these objects measure in the tens of thousands of years. So we don't really get a chance to record these objects for "next time".