You can’t have an oort cloud comet hit the Earth at 160 km/s. The absolute fastest that anything falling from an orbit bound to our sun (oort cloud comets being very lightly bound) in the outer solar system can hit the Earth is about (((1+ square root of 2)* the Earth’s orbital velocity)^2 + Earth’s escape velocity^2)^0.5, or about 73 kilometers per second. This is if it falls from basically infinity (oort cloud distances) to the Earth’s distance from the sun, reaching solar escape velocity at our altitude (square root of two times our orbital velocity) and then hits us head on in our orbit. The true velocity would vary between 73 km/s and 16 km/s with most values somewhere in the middle. Those measured faster velocities came from comets that were falling closer than one AU away from their parent stars.
Granted that’s only a factor of 8 in maximum available energy per unit mass (difference between 73 squared and 160+earth’s orbital velocity + dealing with earth’s escape velocity as above). Still, this has almost certainly happened before over the Earth’s history, many times, on ten to low tens of megayear timescales. Slightly less extreme events would be much more common—events with one tenth the calculated perturbation parameter would be ten times as frequent and come every 1-3 million years. EDITstellar mass lessens this argument a little, this star is relatively large and thus its perturbation parameter is larger than the average stellar pass at this distance
yes, i have no idea how a 25 my old star and disk could have rocks in-falling at that speed, seems like even a gas giant wouldn’t do that, as Jupiter only gives you 30kps,(outside Roche limit).
Still, if Planet 9 is real, and starts slinging stuff around out there, there may be some un-bound bodies in the system soon enough.…
You get infall at speeds like that by falling close to the star—it is the strongest gravitational field in the system and the closer an orbit takes you to it the faster you go. Something falling from the Oort cloud to the surface of the sun reaches a speed of 600 km/s at the moment of impact, and at four solar radii away it is moving 300 km/s. Speed goes down with the square root of distance. Sungrazing comets do this all the time in our solar system, but they are for the most part smallish. The data seeing cometary material moving across the face of another star at that speed was interpreted to mean that there were large numbers of large sungrazing comets falling very close to the star at that point in that star system’s evolution. Keep in mind that at the distances you are looking at, the entire star system is basically a pixel for most instruments so you are seeing the whole thing superimposed over itself.
When two objects interact gravitationally, the maximum physically possible delta V provided to a small object by the big object by a near miss is equal to twice the orbital velocity of the large object. From far away it basically looks like an elastic collision in basic mechanics, and that maximum speed is provided if it comes in and ‘bounces off’ exactly along the orbital vector of the larger object with an initial velocity of nearly zero. Planet 9, if it exists, has an orbital velocity on the order of low single digits kilometers per second and if it sent things into the inner solar system that ‘elastic collision’ would be very much not along the line of its orbit and impart rather less. The biggest thing that could impart velocity changes would be the other star and it would be passing through at 15 kilometers per second, at right angles to the radial direction towards the inner solar system at close approach. Furthermore, near misses would be exceptionally rare. These things are notable for stirring the orbital parameters of very slow moving oort cloud objects by providing a small far-away force for a short time over only a piece of its orbit and allowing some to approach the inner system on orbits with very similar energies rather than adding appreciable energy to the system.
I understand this, and as a young system, you would potentially have a lot more rocks affected by the proposed gas giant, but as you also point out, any un-bounded material should have already been ejected from the system. It is difficult, but obviously not impossible to change parabolas into hyper parabolas to enable these kind of speeds, but they obviously got close enough to hit the roche limit, or simply dissolved like the Christmas Comet of 2014.
Planet 9 is also theorized to be near 90 d(edit:30d) to orbital plane also, so tossing things out where we aren’t looking for them is another hazard in itself. I think the orbital plane of galaxy is out where Pluto is now, (because of the diffuculty of finding secondary targets for New Horizons was made more difficult by background clutter from MW) and 9 is another 40d around the orbital plane, so with a (edit:15k) orbit, there is not a great chance it is going to be relevant in the double influence scenario.
You can’t have an oort cloud comet hit the Earth at 160 km/s. The absolute fastest that anything falling from an orbit bound to our sun (oort cloud comets being very lightly bound) in the outer solar system can hit the Earth is about (((1+ square root of 2)* the Earth’s orbital velocity)^2 + Earth’s escape velocity^2)^0.5, or about 73 kilometers per second. This is if it falls from basically infinity (oort cloud distances) to the Earth’s distance from the sun, reaching solar escape velocity at our altitude (square root of two times our orbital velocity) and then hits us head on in our orbit. The true velocity would vary between 73 km/s and 16 km/s with most values somewhere in the middle. Those measured faster velocities came from comets that were falling closer than one AU away from their parent stars.
Granted that’s only a factor of 8 in maximum available energy per unit mass (difference between 73 squared and 160+earth’s orbital velocity + dealing with earth’s escape velocity as above). Still, this has almost certainly happened before over the Earth’s history, many times, on ten to low tens of megayear timescales. Slightly less extreme events would be much more common—events with one tenth the calculated perturbation parameter would be ten times as frequent and come every 1-3 million years. EDIT stellar mass lessens this argument a little, this star is relatively large and thus its perturbation parameter is larger than the average stellar pass at this distance
yes, i have no idea how a 25 my old star and disk could have rocks in-falling at that speed, seems like even a gas giant wouldn’t do that, as Jupiter only gives you 30kps,(outside Roche limit).
Still, if Planet 9 is real, and starts slinging stuff around out there, there may be some un-bound bodies in the system soon enough.…
You get infall at speeds like that by falling close to the star—it is the strongest gravitational field in the system and the closer an orbit takes you to it the faster you go. Something falling from the Oort cloud to the surface of the sun reaches a speed of 600 km/s at the moment of impact, and at four solar radii away it is moving 300 km/s. Speed goes down with the square root of distance. Sungrazing comets do this all the time in our solar system, but they are for the most part smallish. The data seeing cometary material moving across the face of another star at that speed was interpreted to mean that there were large numbers of large sungrazing comets falling very close to the star at that point in that star system’s evolution. Keep in mind that at the distances you are looking at, the entire star system is basically a pixel for most instruments so you are seeing the whole thing superimposed over itself.
When two objects interact gravitationally, the maximum physically possible delta V provided to a small object by the big object by a near miss is equal to twice the orbital velocity of the large object. From far away it basically looks like an elastic collision in basic mechanics, and that maximum speed is provided if it comes in and ‘bounces off’ exactly along the orbital vector of the larger object with an initial velocity of nearly zero. Planet 9, if it exists, has an orbital velocity on the order of low single digits kilometers per second and if it sent things into the inner solar system that ‘elastic collision’ would be very much not along the line of its orbit and impart rather less. The biggest thing that could impart velocity changes would be the other star and it would be passing through at 15 kilometers per second, at right angles to the radial direction towards the inner solar system at close approach. Furthermore, near misses would be exceptionally rare. These things are notable for stirring the orbital parameters of very slow moving oort cloud objects by providing a small far-away force for a short time over only a piece of its orbit and allowing some to approach the inner system on orbits with very similar energies rather than adding appreciable energy to the system.
I understand this, and as a young system, you would potentially have a lot more rocks affected by the proposed gas giant, but as you also point out, any un-bounded material should have already been ejected from the system. It is difficult, but obviously not impossible to change parabolas into hyper parabolas to enable these kind of speeds, but they obviously got close enough to hit the roche limit, or simply dissolved like the Christmas Comet of 2014.
Planet 9 is also theorized to be near 90 d(edit:30d) to orbital plane also, so tossing things out where we aren’t looking for them is another hazard in itself. I think the orbital plane of galaxy is out where Pluto is now, (because of the diffuculty of finding secondary targets for New Horizons was made more difficult by background clutter from MW) and 9 is another 40d around the orbital plane, so with a (edit:15k) orbit, there is not a great chance it is going to be relevant in the double influence scenario.