Oumuamua may be an alien lightsail?

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  • #26
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I am almost 50 now and for most of my life I think the consensus has been that interstellar objects were highly speculative and extremely rare and that we should not really ever expect to see any. I guess sort of like intergalactic objects might be regarded now. Sure now it is easy to point to past theories that mostly only science fiction authors paid attention to and say well of course. So far the predictions that we would start seeing more of these objects now that we are looking for them have failed.

The Ice Limit by Douglas Preston and Lincoln child featured an interstellar asteroid and I remember how far fetched and speculative it seemed when I read it at the time. Of course being the entertaining but trashy but fun writers that they are they pushed it even farther than that but it was just science fiction until now. Were there really a lot of scientists predicting we would start seeing these things? I guess I should just check an old astronomy textbook, but I think not. I think the next editions of many astronomy and astrophysics textbooks are going to have the word Oumuamua in them now. Of course if we do catch up with this thing one day and it is a million year old ship or monolith or ice sculpture or something even stranger then interstellar asteroids will remain in the realm of science fiction.
 
  • #27
stefan r
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I'm sorry, but I can't find the image I saw months ago. I think it was a radar image; could Arecibo resolve it?
no resolution.

NASA released an artist's image. That is the official picture.
 
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  • #28
Sanborn Chase
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If the difficulties of doing so could be surmounted, could an Earth-based sub-millimeter VLBI system resolve it? I feel sure many of the variables of this case present a formidable challenge for such an array to do so, but would the sheer resolving power exist? Thanks.
 
  • #29
stefan r
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If the difficulties of doing so could be surmounted, could an Earth-based sub-millimeter VLBI system resolve it? I feel sure many of the variables of this case present a formidable challenge for such an array to do so, but would the sheer resolving power exist? Thanks.
If oumuamua had 2 cell phones broadcasting the vlbi would be a good system for figuring out where they were with respect to each other. I think they can get down to a milliarcseconds. A milliarcsecond would have given 2 pixels the long way and would be back to 1 pixel on short side.
I am not sure how much radio wavelengths were bouncing off of Oumuamua. The signal needs to exceed the background noise.
 
  • #30
the fact that it is the first and after an entire year still the only interstellar object we have ever seen
Oh boy, *entire year* and we didn't see another one? I'm sure you know that in the last 400 years, this one is the first. Why are you surprised we didn't see two in 1 year timespan? Telescopes do improve, but not THAT fast.

If it is natural it is entirely unlike anything we have seen before. It is not a comet or an asteroid and it is much too small to be a planetoid.

We dont have any way to explain how a natural object could present this way. We just dont. The data is just not consistent with any natural explanation.
What are you talking about?
Its behavior is explained quite well by a theory that it's an oblong chunk of rock.
 
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  • #31
I am almost 50 now and for most of my life I think the consensus has been that interstellar objects were highly speculative and extremely rare
No, this wasn't the consensus. Interstellar objects were expected to be seen inevitably. A number of similar objects probably flew through our system undetected in the last ~200 years. As large survey telescopes become more numerous, we finally saw one.
 
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  • #32
Sanborn Chase
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Could a VLBI system be used to "paint" such an object? Has anyone used the system as a radar?
 
  • #34
sophiecentaur
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No, this wasn't the consensus. Interstellar objects were expected to be seen inevitably. A number of similar objects probably flew through our system undetected in the last ~200 years. As large survey telescopes become more numerous, we finally saw one.
The advent of digital imaging and the use of space telescopes had meant that the flow of useful data has increased many orders of magnitude. Even the management of the data has improved and so any worker who wants a certain type of data can find it and analyse it. It's not surprising that new objects are being found on an almost daily basis where they were found very infrequently in the days of Messier and his pals.
 
  • #35
Sanborn Chase
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Sophiecentaur said"...so any worker who wants a certain type of data can find it and analyse it."
Whoa! I think he's correct about our increase in data and our ability to organize and analyse it, but is it that simple? Could the bane of the Information Age be searching for that last bit of confirming data from the previous work of others?
 
  • #36
sophiecentaur
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Sophiecentaur said"...so any worker who wants a certain type of data can find it and analyse it."
Whoa! I think he's correct about our increase in data and our ability to organize and analyse it, but is it that simple? Could the bane of the Information Age be searching for that last bit of confirming data from the previous work of others?
If you want to see a certain piece of sky, I think that it wouldn't be too hard to find a number of images of it. Large telescope "owners" gather far more data than they are capable of analysing on their own and are only too pleased to make it available (at a price, no doubt. The running costs are quite high. Windolene is not cheap!
 
  • #37
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Please consider an unbound interstellar object approaching our sun with initial impact parameter D measured in AU

If the body has high positive total energy, it won't deflect very much from its initial path as it approaches the sun... And so we would overlook most of such objects, as they traveled quickly through the outer reaches of our system (unless they happened to be aimed straight at the sun, which is unlikely, the differential capture cross section increases as 2 pi R dR)

So the only unbound interstellar objects that we are likely to observe are those with low or zero total energy, because only they would be deflected appreciably towards the Sun, into the inner solar system, where we would be able to detect them

Such objects would move along approximately parabolic trajectories

Have people observed parabolic trajectory objects? Could any of them possibly be interstellar in origin also?
 
  • #38
davenn
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Have people observed parabolic trajectory objects?
of course .... just about every comet


Could any of them possibly be interstellar in origin also?
well, Oumuamua, is considered the first one
 
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of course .... just about every comet




well, Oumuamua, is considered the first one
technically, a parabolic trajectory is not localized to the Sun's vicinity ?

Knowing what's actually out there would be valuable info for Project Breakthrough Starships & such
 
  • #40
LURCH
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technically, a parabolic trajectory is not localized to the Sun's vicinity?
I don’t know if you are unsure, or the question mark is a typo, but you are correct; a parabola is an escape trajectory. Comets have an elliptical orbit, just one with a high degree of eccentricity.

https://www.eso.org/public/usa/news/eso1820/

It appears that the international team studying the object have concluded that outgassing is indeed the cause of the acceleration.

Now that we have the ability to detect extrasolar objects passing through our system, I’m really looking forward to seeing what we find next. I’ve heard estimates that, every year, at least one object passes within 1’AU of the Sun, and up to 10,000 pass within the orbital radius of Neptune. I guess now we’ll start to see if those estimates are anywhere near accurate.
 
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I don’t know if you are unsure, or the question mark is a typo, but you are correct; a parabola is an escape trajectory. Comets have an elliptical orbit, just one with a high degree of eccentricity.

https://www.eso.org/public/usa/news/eso1820/

It appears that the international team studying the object have concluded that outgassing is indeed the cause of the acceleration.

Now that we have the ability to detect extrasolar objects passing through our system, I’m really looking forward to seeing what we find next. I’ve heard estimates that, every year, at least one object passes within 1’AU of the Sun, and up to 10,000 pass within the orbital radius of Neptune. I guess now we’ll start to see if those estimates are anywhere near accurate.
That would translate to 10,000 objects per 1-10 thousand cubic AU or so (given an average relative velocity of order tens of km/s)?

One object per cubic AU would be about 8,000 trillion objects per cubic parsec, comparable to the figure quoted in the PBS space time episode about Oumuamua... E16 objects x e10kg per object = Neptune mass... Doesn't seem implausible
 
  • #42
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Oh boy, *entire year* and we didn't see another one? I'm sure you know that in the last 400 years, this one is the first. Why are you surprised we didn't see two in 1 year timespan? Telescopes do improve, but not THAT fast.
Some people are arguing that interstellar objects like this, whether natural or artificial, are quite common and that only now do we have the tech to see them and now that we can we should be seeing as many as 10 per year. My recollection is that most astronomers were not really expecting to see them either, but that may be wrong. Were people really searching for interstellar asteroids before? Until we see another one I am going to continue to assume that they are exceedingly rare to nonexistent. If we do see another one it will certainly make the artificial origin idea seem less plausible, at least to me.


What are yzou talking about?
Its behavior is explained quite well by a theory that it's an oblong chunk of rock.
A rock that can accelerate away under its own power you mean. A cigar shaped one. No I dont think we have seen anything like that before outside of science fiction novels. An object with an interstellar trajectory that makes a beeline for the Goldilocks zone and with a NASA-like perihelion and with a strange shape and unusual albedo and that can accelerate. Not an asteroid at least as we know it.
 
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Some people are arguing that interstellar objects like this, whether natural or artificial, are quite common and that only now do we have the tech to see them and now that we can we should be seeing as many as 10 per year. My recollection is that most astronomers were not really expecting to see them either, but that may be wrong. Were people really searching for interstellar asteroids before? Until we see another one I am going to continue to assume that they are exceedingly rare to nonexistent. If we do see another one it will certainly make the artificial origin idea seem less plausible, at least to me.




A rock that can accelerate away under its own power you mean. A cigar shaped one. No I dont think we have seen anything like that before outside of science fiction novels. An object with an interstellar trajectory that makes a beeline for the Goldilocks zone and with a NASA-like perihelion and with a strange shape and unusual albedo and that can accelerate. Not an asteroid at least as we know it.
Please do remember, we live in our own star's HZ...

and can only observe Oumuamua like objects when they basically buzz our planet... which is in our own HZ...

your words are true, and can be explained purely by current "selection bias"

To fully justify your conclusion, we'd have to task the cameras onboard Voyager 1, 2 and New Horizons to scan the skies for interstellar objects... and fail to observe any

Only then would you be truly justified in suggesting that Oumuamua was somehow suspiciously unique, or something like that

Possibly, our long range probes would detect innumerable other objects barreling through the outer solar system (which would suggest the opposite, that interstellar objects are quite common)
 
  • #45
sophiecentaur
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Aliens are the modern equivalent to Ghosts, magic and Polytheism, I think. The more you look and the wider your 'acceptance window', the more likely you are to find possible evidence. In addition to the vast distances involved and the limited time window for traces of a 'civilisation' to be intercepted by humans, there is the equally huge possible variation in cultures and brain functions. We could be receiving all sorts of signs and messages but just not recognising them. Otoh, we might well not and there may be nothing worth our attention.
 
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  • #46
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Please do remember, we live in our own star's HZ...

and can only observe Oumuamua like objects when they basically buzz our planet... which is in our own HZ...

your words are true, and can be explained purely by current "selection bias"
Well that's the point; the chance of an interstellar object buzzing our planet should be so statistically rare, that if one does so it automatically becomes suspicious. Add in the light-curve, no outgassing and non-grav acceleration, and I think the odds favor the theory that this is artificial.
 
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  • #47
sophiecentaur
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it automatically becomes suspicious.
No more suspicious than a suggestive pattern of tea leaves in a cup. If you really want anything to be true then it's not hard to find some apparent evidence - as long as you ignore what our understanding of statistics is telling you.
If we started to see droves of them, we would all give the idea some credence. Shame we can't just run after it and fetch it to Earth for an examination.
 
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  • #48
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Well that's the point; the chance of an interstellar object buzzing our planet should be so statistically rare, that if one does so it automatically becomes suspicious. Add in the light-curve, no outgassing and non-grav acceleration, and I think the odds favor the theory that this is artificial.
https://www.businessinsider.com/har...ar-object-alien-spacecraft-solar-sail-2018-11

Rob Weryk, who first discovered Oumuamua in 2017.
Weryk: there's no reason to think Oumuamua is anything but a natural object.
So we think Oumuamua still has ice and the sublimating ice gives it a small tiny kick that gravity alone wouldn't account for, but that the dust it has is much larger than what comets typically have. And so we just don't see that from the ground.
 
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Rob Weryk, who first discovered Oumuamua in 2017.
Weryk: there's no reason to think Oumuamua is anything but a natural object.
So we think Oumuamua still has ice and the sublimating ice gives it a small tiny kick that gravity alone wouldn't account for, but that the dust it has is much larger than what comets typically have. And so we just don't see that from the ground.
But there's just no example in the literature of a comet giving off 'larger dust' without also giving off gases and water. The scientists are inventing 'natural' reasons in order to avoid even mentioning the dreaded A word. Unfortunately the soonest we could possibly reach it is 2036 so it seems likely to remain a mystery.
 
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  • #50
sophiecentaur
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The scientists are inventing 'natural' reasons in order to avoid even mentioning the dreaded A word.
If "scientists" went haring after every hint of aliens / magic / supernatural, you can be sure we would still be at the pre-enlightenment stage of progress in the subject.
You will laugh at the magic-based ideas that were around about Medicine just over a hundred years ago in the West (and still are in some parts of the developing world) If you cannot be objective and rational, there is no help for you, I'm afraid.
There are plenty of fanciful conversations to be had on the Internet about such things but not on PF.
 
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