Oh no! Another alien probe

[Anomalocaris]

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.

The most effective encounter for using Jupiter to boost an object out of the solar system should have the following parameters:  1) the object’s heliocentric orbit should have substantial eccentricity.  2) when the object enters jupiter’s Gravitational sphere of influence, it should be nearing the perihelion of its own heliocentric orbit.   3). once inside jupiter’s Sphere of influence, the object’s  Jovecentric orbit should place its perijove as close to jupiter’s Cloud tops as possible, and the perijove should be over the center of the trailing hemisphere of Jupiter.  

These parameters are hard to achieve when using sling shot maneuvers to boost a spacecraft from earth to solar escape velocityies.  1. The limits on launch weight puts limit on how much delta-V the booster can give the spacecraft as it leaves earth orbit.  So a high eccentricity heliocentric orbit is not easy to achieve without some preliminary gravitational sling shot with either earth itself or Venus.  2) because earth is interior to Jupiter, space craft from earth will approach Jupiter near the apohelion of their heliocentric orbit, not the perihelion.  3) putting perijove very close to jupiter’s Cloud top is risky, because it puts the spacecraft deep inside jupiter’s Radiation Belt, and a slip up could plung the spacecraft into Jovian atmosphere.  In addition, the placement of apojove is not concerned with boosting the spacecraft to the highest possible escape velocity from the solar system, but making sure the spacecraft will intersect with its next mission objective.

This is why slingshot maneuvers used by NASA do not exhibit the maximum power of Jupiter in kicking something out of the solar system.

It is true that if Jupiter is to encounter a dense swarm of objects in relatively randomized heliocentric orbits, relatively few of the objects will meet with Jupiter on ideal solar escaping slingshot terms.  Most of them won’t be boosted out of the solar system.  Instead they will be scattered around inside the solar system in more randomized orbits until they collide with a major body like a planet, jupiter, or the sun.  A few of them may be lucky enough to have a second fortuitous encounter with Jupiter that will boost them out of the solar system.

But the point I am trying to make is during the formative stages of solar system and its first 500million years or so, sun baked objects that has lost all their volatiles may have been so abundant in the inner solar system that even if only a tiny percentage of them encountered Jupiter on the right terms to get boosted out of the solar system, the total number of objects thus boosted out may have been enormous and have been equal or greater than the total number of objects since lost from the Oart cloud.

It is also true that if Jupiter is the primary agent in ejecting inner solar system objects, then the hyperbolic eccentricity of the escapees are unlikely to be significantly in excess of 1.   Jupiter simply isn’t massive enough and also too close to the sun to boost objects to eccentricities much greater than 1.0.   But, our observation of extrasolar planetary systems suggests plenty of systems where there are planets substantially more massive than Jupiter.    

The limits in our observation technique biases our samples to planets that are close to the parent star.  So we don’t know how likely are planetary systems to have a super Jupiter farther away from the parent star than our own Jupiter.

But what is clear is if solar system has a planet say, 10 times the mass of Jupiter located at 50 or 100 AU, that planet would be capable of throwing objects out of the solar system at significantly higher eccentricities.   This means escapees from these systems can have substantial residual net velocity compare to their origin stars after they’ve escaped.

Now, in addition to excess velocity of escape, there is the initial velocity of their origin system to consider.  our solar system’s follows a pretty circular orbit about the center of the Milky Way with an orbital speed of about 250km/s.   This means at our distance from the center of Milky Way, any object with speed falling in the range of less than square root of 2 times our own orbital velocity (at our distance anything faster will escape the Milky Way), to greater than our velocity divided by square root of two (at our distance anything slower will fall into the core of Milky Way) will remain in stable orbit about the Milky Way at our distance.  This is an enormous range, about 180km/s to 350 km/s.   This means even if we only consider stars that are in the plane of the Milky Way and orbit about the Milky Way in the same direction as the sun, we can still encounter stars with relative velocities to the sun of up to 100 km/s.   This means any escapee from such a star can enter the sun’s gravitational sphere of influence with an initial velocity of up to 100 km/s plus whatever excess escape veology they achieved during their escape.

Now an escapee object from a star in a retrograde orbit can potentially enter our solar system at up to 600 km/s.