RE: Oh no! Another alien probe
December 15, 2017 at 8:31 pm
(This post was last modified: December 15, 2017 at 8:37 pm by Jehanne.)
If the object formed in another star system's Ort cloud, then, as I have stated, it should have likely had a coma as it passed by. Of course, the object could have been an asteroid from another star system, also, but consider the following from the Voyager spacecraft:
https://voyager.jpl.nasa.gov/mission/status/
Relative to the Sun (which has a galactic velocity of 250 km/s), the Voyagers themselves are moving 15 km/s relative to the Sun, and that's after two gravity assisted boosts for Voyager 1 and another two for Voyager 2, beginning with a large rocket for each!
And, so, getting enough of a delta-v from another star system that is closer to the Galactic center (we are about two-thirds of the way out), and hence, in a lower energy orbit would require a huge amount of energy for the large delta-v. I haven't done the calculation (which, would need to involve estimates of dark matter), but it would likely involve something much greater than the kinetic energy given to the Voyagers, especially, given the large masses involved. And, so, yes, I agree with you that a small delta-v would be enough to free an object from our solar system's Ort cloud or that of another star, but to get, in essence, a transfer orbit, from one star system to another, a much larger (or, smaller, to go towards the galactic center) delta-v (and, hence, much more energy, either gained or lost) would be required.
https://voyager.jpl.nasa.gov/mission/status/
Relative to the Sun (which has a galactic velocity of 250 km/s), the Voyagers themselves are moving 15 km/s relative to the Sun, and that's after two gravity assisted boosts for Voyager 1 and another two for Voyager 2, beginning with a large rocket for each!
And, so, getting enough of a delta-v from another star system that is closer to the Galactic center (we are about two-thirds of the way out), and hence, in a lower energy orbit would require a huge amount of energy for the large delta-v. I haven't done the calculation (which, would need to involve estimates of dark matter), but it would likely involve something much greater than the kinetic energy given to the Voyagers, especially, given the large masses involved. And, so, yes, I agree with you that a small delta-v would be enough to free an object from our solar system's Ort cloud or that of another star, but to get, in essence, a transfer orbit, from one star system to another, a much larger (or, smaller, to go towards the galactic center) delta-v (and, hence, much more energy, either gained or lost) would be required.
