It is thought that Oumuamua may have been ejected from its home system at high velocity, between about 6 and 16 miles (10 and 25 km) per second, and this high speed may be because it originated in a binary/trinitary star system with no large planets to assist in the acceleration. Such a system would have a hard time developing any planets at all, with most orbiters remaining small, elongated, with a somewhat “fluffy” consistency. The parent stars would have played a kind of gravitational ping-pong with their bits of debris, flinging particles in all directions.

As it departed our system Oumuamua appeared to pick up speed. It is supposed that solar wind and normal outgassing by the visitor had caused this acceleration. It was also thought that Oumuamua might be incredibly thin with a large surface area, acting as a natural solar sail. For any of this to occur, the “rock” would have to be of comet-like material, extremely porous and light, and capable of expelling approx. 2.2 pounds (1 kilogram) of material per second just as our local family of comets do. …And if it were actually hollow, the idea of outgassing as an accelerator works quite well.

Unfortunately our infrared-seeking Spitzer Space Telescope tracked the departing visitor for 30 hours, but no outgassing was observed … or at least there was nothing the telescope could see.

These are just my notes from reading through the astronomy.com February 2020 issue of ‘Oumuamua: our first interstellar visitor.

Read through the story and see that Oumuamua was not alone. Our latest interstellar visitor is called 2I/Borisov for amateur astronomer Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. 2I/Borisov had been seen moving at approx. 93,000 mph (150,000 km/h), faster than expected for an object that was still roughly 2.8 AU from the Sun. It has since crossed solar perihelion at 2 AU distance on December 8, 2019, and continued on its way outsystem, judged to remain observable by our best technologies through October of 2020.

With the 2I/Borisov event, there is a definite comet-like tail.

Every planet in the solar system holds a series of lagrange points (Pluto is likely too small to have much more than L1 and L2 as feasible navigable traps) which could handle the orbit of a small fleet of sleeper satellites, each watchful, each networking current data to other sleepers around the solar system, each fully fueled and ready to pounce.

Interstellar visitors would likely be traveling at much higher speed that our current bevvy of comets and asteroids (100,000 mph), simply to hold and maintain a stellar escape velocity, even faster than our own interstellar probes. They would come as a flash across the system.

There’s another issue, which refers to an issue we brought up here recently, any orbit which is essentially static (not Keplerian) would require some tricky maneuvering, slingshotting and other gravitational tricks to set up. Sure, we could place a satellite in a static (non-orbital) location so that its distance high up the sun’s gravitational well would provide the potential energy advantage needed to initiate a mad chase across the solar system after an ISO. Solar sails could be used to keep the craft in position with minimal energy expenditure, but getting it into that spot would probably be as energy expensive as our recent Solar Explorer mission we discussed a few weeks ago. See the comments for the following thread Latest Earth Flyby . . . by DanS April 11, 2020 3:14 pm

This project might make sense if you knew way ahead of time where, when, how fast and how close the ISO was coming, but to have a constellation of satellites in position to handle an approach with only a slight warning would be expensive. I expect it would require a constellation of at least dozens, and possibly hundreds, of statites, and this fleet would have to be managed, that is, launched, tested, maintained, exercised, and periodically updated and replaced as new technologies were developed and the birds wore out or became obsolete. And of course, the infrastructure to maintain this squadron (the “Mission Control”) would be extensive and complex–much more expensive than a planetary defense system designed to ID and calculate orbits for potential earth colliders in the ecliptic plane. That’s where we should be spending our money. Not only is the problem easier, it it has the potential for saving lives.

And how often do these outsiders buzz our solar system, anyway? We’ve seen only two over the last few years, but this could be just sheer luck. They might come through hundreds, or thousands, of years apart. We have no guarantee they are frequent visitors.

This sounds like just another engineering boondoggle to me: not necessarily scientifically impossible, just way too complex and expensive to be actually worthwhile.