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Interstellar Interloper, Coming in from the great beyond
alan
post Dec 27 2017, 10:22 PM
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Years ago someone here estimated that the distance between Oort cloud objects would be greater than 1 AU, which would make it very difficult for a spacecraft to find one.
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HSchirmer
post Dec 29 2017, 08:47 PM
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QUOTE (alan @ Dec 27 2017, 10:22 PM) *
Years ago someone here estimated that the distance between Oort cloud objects would be greater than 1 AU, which would make it very difficult for a spacecraft to find one.


So, probably need to wait till aafter 2069, when NASA is hoping to top the 100th anniversary of the lunar landing with a probe to Alpha Centauri.

Some current ideas and solar sails are described at

https://tviw.us/2017-presentation-video-archive/
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nprev
post Dec 30 2017, 10:07 AM
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ADMIN MODE: Discussion is drifting off-topic pretty rapidly here; let's please restrict future posts to 1I/2017 U1 ‘Oumuamua (though there may be little more to discuss.)


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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HSchirmer
post Dec 30 2017, 03:44 PM
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QUOTE (fredk @ Dec 21 2017, 05:47 PM) *
QUOTE (Gerald)
Even a very small gravity assist of an inner planet could add sufficient kinetic energy that the object would escape, due to the multiplication by the Oberth effect.

Only if the object could provide thrust, since the Oberth effect refers to the efficiency of thrust. So are you thinking of cometary jets? What delta v would be realistic?

Also, we know the body's asymptotic velocity: around 26 km/s relative to the sun, much higher than 100 m/s, though it's not clear what you meant by that.


Suppose I1 IS a shard of a metal protoplanet, something like Kleopatra


shouldn't something metal going 26 km/s through the solar magnetic field be generating one helluva electric field?
And, given that it's 300 meters long and spinning, generate wake currents?


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Gerald
post Jan 1 2018, 09:48 PM
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The interplanetary magnetic field is on the order of nano teslas. Faraday's law says, that the electromagnetic induction is proportional to the change of the magnetic flux.
Although the absolute value of a field a priori doesn't tell much about its change, it's reasonable to assume, that the interplanetary magnetic field doesn't change rapidly enough with the path of the interloper to induce currents strong enough to cause effects that can be measured easily from a distance on a scale of astronomical units.

Btw, regarding Oort objects: Once you get above some 10s of millions of years for one orbital period, the orbit is likely to be instable, and modified by nearby stars or interstellar gas clouds.
So, from a probabilistic point of view, I'm still inclined to favor an outer Oort-like object from another star as one of the most likely scenarios for the origin of 'Oumuamua. Some of these Oort objects might have been scattered from the inner part of the planetary system. But I think, that it's much more plausible, that most of these objects are forming very early during the formation of a planetary system, without ever coming closer to the central star than a few hundreds of AUs. If they do, they are likely to be ejected from the planetary system due to some more or less subtle gravity assist by an inner planet, no matter what orbital history they underwent before. Another possible outcome is a capture in the inner planetary system, and a destiny as a more or less short-period comet.
These disturbances of orbits of Oort objects into a trajectory close to the central star should be pretty unlikely for a single object, since otherwise the Oort cloud would be short-lived, and would have collapsed within a fraction of the life-time as of yet of our solar system.
The only source for Oort objects would then be captures of ejected Oort objects of other planetary systems.
But the low probability summed over possibly billions of objects results in an Oort object visiting the inner planetary system every few or several years.

The only weak point in the scenario of an outer Oort cloud of another planetary system as the source of 'Oumuamua I see, is the lack of sublimated volatiles or accompanying dust. Oort objects should initally be rich in supervolatiles. Removing them completely, including all loose dust, from the outer several cm without disrupting the object thermally, or adding a volatile-free encoding to an Oort object, is the portion of the scenario that doesn't yet look fully conclusive.
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