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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.)


--------------------
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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Holder of the Tw...
post Jan 20 2018, 09:48 PM
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Been planning for a while to get these MPECs in, finally getting around to it.
Here are all the Minor Planet circulars I'm aware of pertaining to 'Oumaumau:

2017-U181
2017-U183
2017-U185
2017-U234
2017-U263
2017-U265
2017-V01
2017-V13
2017-V17
2017-V38
2017-V62
2017-V63
2017-W75

The circular 2017-U234 gives the residuals for all the observations up to that point. They show that all the observations in the initial announcement in 2017-U181 were sufficiently precise (none in error by more that 1.5 arc sec) that they were all useful in computing the preliminary orbit. Since an amateur observer's contribution was called in question after the earliest reports, in retrospect they were good enough.
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JohnVV
post Jan 22 2018, 12:50 AM
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with many projects going on , i was able to do some work on a texture for the mesh
-- Artistic and all done in Blender nodes
Attached Image

and
Attached Image
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Paolo
post Jan 22 2018, 06:10 PM
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there was a good summary of what we have learned from the first interstellar object at last week's SBAG meeting
https://www.lpi.usra.edu/sbag/meetings/jan2...-35am_Meech.pdf
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dtolman
post Feb 6 2018, 04:46 PM
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Radar Observation would have answered a lot of questions regarding this objects shape and disposition - but I'm not really familiar with what the limitations are with an object of that size and speed - would it have been possible to do radar observations back in October if there was time to plan for it/if it was detected earlier? Or would it have needed to be a lot closer to the Earth to get even crude information regarding its size and shape?
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Holder of the Tw...
post Feb 6 2018, 06:16 PM
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The Goldstone radar never really had a chance with this one. 'Oumaumau was probably too small to even be detected at its closest approach. Certainly too small to get anything other than just a basic signal return that would barely pop out of background noise. Arecibo theoretically could have seen it around October 20 when it moved into the extreme southern end of what that telescope could observe, but it would have been a very short window and not much of a signal either, as it was rapidly moving away at that point. In any event, the orbit of 'Oumaumau at that point was too uncertain, and the notice was too short.
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JRehling
post Feb 7 2018, 10:47 AM
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Radar signal strength drops off with the fourth power of distance. Oumaumau was at its closest 0.22 AU from Earth. That's closer than Venus gets to Earth, and we've made good maps of Venus with radar, but Oumaumau is smaller than the resolution of the terrestrial-based radar maps of Venus, so we'd have gotten some information of the entire body and how that varied over time, but no resolving power. As noted, the time window was short, and I guess the world wasn't on red alert. Moreover, this was only weeks after Hurricane Maria pounded Puerto Rico, and the Arecibo facility was damaged.
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Explorer1
post Feb 8 2018, 01:09 AM
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It was around 60 lunar distances at closest approach; this website shows a whole bunch of radar observed comet and asteroids, for comparison:
https://echo.jpl.nasa.gov/asteroids/

I doubt it could have been very well resolved even if it had been spotted while inbound, but all the more need to keep our scopes peeled; where there's one there will be more...
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Explorer1
post May 21 2018, 02:39 PM
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And speaking of more.... https://academic.oup.com/mnrasl/article-abs...edFrom=fulltext

More accessible than 'Oumaumau, but a retrograde orbit makes rendezvous difficult without a gravitational assist. Is it possible to confirm interstellar origin from the ground, compositionally?

This article has some more skeptical opinions; no one has actually simulated the capture event yet: https://news.nationalgeographic.com/2018/05...-space-science/
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JRehling
post May 21 2018, 07:38 PM
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It seems exceedingly unlikely that we would confirm extrasolar origin by remote sensing of composition. Tholins and organics are hard to identify in detail in the first place. Simple molecules and ices would be the same here as anywhere else. And none of those things are easy to measure quantitatively through spectral analyses alone.

The thing we'd probably most benefit from in probing any extrasolar interloper would be the detailed isotopic composition. And for that we'd probably need a landing + in situ analysis.
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