Question Orbits of Interstellar Objects

[newworldsexplr]

There have been two confirmed observed interstellar objects in our solar system so far as I know, the asteroid Oumuamua and Borosov's Comet. Both of these objects were deflected by the sun and sent out in substantially different directions from which they came. My question is could an interstellar object still be in an elliptical orbit and have high enough speed to escape our solar system? Would an interstellar object that appears to return mostly in the direction from which it came into our solar system be significantly suspected of being an artificial or alien object or could this happen naturally?

 

[billslugg]

All interstellar objects that enter the Solar System have hyperbolic orbits that do not close on themselves. All elliptical orbits close on themselves and thus remain in the Solar System.
But there is an exception. In a three body system, one of the bodies can be ejected from the system. Say, for example, Mercury is zipping around the Sun. I am an object coming in from far away and I catch up to Mecury and pass it. As I am catching up to it, I am gaining energy at Mercury's expense. Then suddenly Mercury curves off to the left and I am no longer in its gravitational well thus I maintain my newly found energy, which is now enough to eject me from the Solar System.

 

[Pogo]

By definition, an elliptical orbit has an apoapsis with reference to the barycenter of the system, therefore is tied to the system. Only if the orbiting body receives kinetic energy in the direction of travel, boosting its velocity would it then escape, such as the slingshot described by @billslugg, or a propulsion system. As we observe an object in a hyperbolic orbit, we can compare its orbit with a similar Keplerian orbit. If it deviates, we would then seek a force which may have altered the orbit, perturbations, outgassing, solar light pressure, etc. A scientist would consider intelligent motion only if there is independent data to support it and all other sources have been eliminated.

 

[Wolfshadw]

Correct me if I'm wrong, but isn't an "interstellar" object, something that escapes the sphere of influence of a stellar object? If it's classified as an interstellar object, then once it escapes, it's not coming back (unless it's acted upon by at least one other stellar object).

By that logic, interstellar objects do not "orbit".

-Wolf sends

 

[Helio]

Correct me if I'm wrong, but isn't an "interstellar" object, something that escapes the sphere of influence of a stellar object? If it's classified as an interstellar object, then once it escapes, it's not coming back (unless it's acted upon by at least one other stellar object).

By that logic, interstellar objects do not "orbit".

Yes.

It's all about energy. If you drop a ball to a hard floor, due to friction caused by the elstatic reaction with the ground and, also, that of the air, it cannot bounce back to its orginal height. [Imagine if the ball actually bounced higher - Hollywood did and flubber was born! Nice flick.]

Comets don't suffer with energy losses due to friction. They simply gain KE as they lose PE on the trek inward, then the reverse happens on the way out. Just like a kid coasting down a hill on a bike will be able to coast up the hill if the climb is less than the fall (due again to friction).

When a comet comes from outside the Sun's gravity well, it will "bounce" back to a height from wence it came, though with an altered course. It can't have an elliptical orbit since these, by definition, require an object to always return, thus never escaping the Sun's gravity.

The KE it will have will be both the energy (velocity) it had when it came under the Sun's influence + the KE it gains from the fall. Therefore, it will always have enough KE to escape.

However, as usual, there are some side details worth mentioning. If something big (e.g. planets) gets in the path of any object, the object will either gain or lose energy for the reasons billslug stated. If the object is traveling prograde it comes from behind the path of the planet, it will gain some extra velocity due to the speed of the planet in its orbit.

So the opposite is true, if our comet is traveling retrograde and passes by, say Venus, then the orbital velocity of Venus will have an impact on the comet causing it, and Venus for that matter, to slow down. [Note that Jupiter has many small objects in retrograde orbits around it for this reason.]

Of course, they have to be close to one another.

Space probes take full advantage of this both to speed up and to slow down, as needed. [Of course, I know you know this, but it may bring greater clarity for others.]

This is why the question of Leonard's hyperbolic orbit is so interesting. It, apparently, came from" sitting still" in the inner Oort Cloud, so how did it come with enough velocity to give it escape velocity. It had to get a push.

 

[newworldsexplr]

By definition, an elliptical orbit has an apoapsis with reference to the barycenter of the system, therefore is tied to the system. Only if the orbiting body receives kinetic energy in the direction of travel, boosting its velocity would it then escape, such as the slingshot described by @billslugg, or a propulsion system. As we observe an object in a hyperbolic orbit, we can compare its orbit with a similar Keplerian orbit. If it deviates, we would then seek a force which may have altered the orbit, perturbations, outgassing, solar light pressure, etc. A scientist would consider intelligent motion only if there is independent data to support it and all other sources have been eliminated.

Hi Pogo, good response and that from Bill Slugg. How long do you think it will be before astronomers can observe interstellar objects on a more regular basis and get a better idea what is normal compared to Oumuamua or Boresov's Comet?

 

[billslugg]

Here is a chart showing how the discoveries of near Earth objects are progressing. We are finding more and more all the time.
Discovery Statistics (nasa.gov)

 

[Pogo]

Let’s think of it this way. An object in orbit about the galaxy far from other objects is by definition, an interstellar object. Then it encounters a star system such as ours. It enters a hyperbolic orbit within the system likely altering its galactic orbit, then it leaves on to new stomping grounds. It’s still an interstellar object, but from the time the system’s gravitational influence outweighs the galactic gravity until the object is back to interstellar gravity, the object can be said to be an interstellar visitor. If, by chance it is captured into solar orbit or that of another body, it’s no longer an intersteller object, but a new member of the system.

 

[Pogo]

We can see only a handful of Kuiper objects and only the biggest ones, and none of the Oort objects, as compared to our inner system location, those are far away and too faint. Intersteller passers by are just too small and faint, and too much sky to cover it all. We would need many scopes that make James Webb look like a backyard scope stationed at the outer Oort Cloud to have any hope to catch a few of them.

 

[billslugg]

I believe they have found a whole bunch of interstellar planets using gravitational lensing. No image of the object just a blip of starlight that says something passed in front of a star.

 

[Pogo]

A number of planets orbiting stars and even a couple of rogue (intersteller) planets have been found by the occultation method.