Oumuamua may be an alien lightsail?

[nikkkom]

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.

 

[Sanborn Chase]

Could a VLBI system be used to "paint" such an object? Has anyone used the system as a radar?

 

[TEFLing]

https://www.nature.com/articles/s41586-018-0254-4

 

[sophiecentaur]

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.

 

[Sanborn Chase]

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?

 

[sophiecentaur]

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!

 

[TEFLing]

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?

 

[davenn]

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

 

[TEFLing]

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

 

[LURCH]

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.

 

[TEFLing]

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

 

[metiman]

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 don't 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.

 

[TEFLing]

https://www.forbes.com/sites/bruced...tellar-objects-now-in-our-outer-solar-system/

 

[TEFLing]

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 don't 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)

 

[sophiecentaur]

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.

 

[SLockhart]

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.

 

[sophiecentaur]

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.

 

[TEFLing]

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...-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.

 

[SLockhart]

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.

 

[sophiecentaur]

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.

 

[TEFLing]

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.

the anomalous acceleration of Oumuamua decreased as 1/r² exactly as with numerous other comets due to radiation pressure & radiation-induced off-gassing.

Is it impossible, that the object was actually very small, meteoroid in size... and that it was off-gassing, was producing a (small) coma, which is the only reason we observed it at all? a 1m object off-gassing reflects as much light and IR as the 100m object inferred from SPITZER ?? Especially if only one side of the object retained volatiles to off-gas ? Such that the coma dwindled down each time the snowy side swung into shadow ??

 

[DrStupid]

Is it impossible, that the object was actually very small, meteoroid in size... and that it was off-gassing, was producing a (small) coma, which is the only reason we observed it at all?

If this would be the case, how would you explain the missing tail and the oscillating brightness?

 

[TEFLing]

If this would be the case, how would you explain the missing tail and the oscillating brightness?

Especially if only one side of the object retained volatiles to off-gas ? Such that the coma dwindled down each time the snowy side swung into shadow ??

 

[Vagn]

If this would be the case, how would you explain the missing tail and the oscillating brightness?

We've never seen an interstellar object before, and don't know much of the history of 'Oumuamua, i.e: How old is is?; How long is it since it was ejected from its parent star (if it had one)?; Has it passed through any dust clouds before entering the solar system?; How many other solar systems has it passed through?

If a comet had traveled for considerable periods of time in interstellar space, it is entirely possible that the volatiles were heavily depleted by interactions with radiation, such as sputtering or by sublimation earlier in its history. Alternatively, the comet may be covered with a thick layer of dust. The age of craters in our own solar system is broadly correlated with the age of the crater in question, so it is to be expected that an old object may be covered in a lot of dust. Thus, the varying brightness may be related to a more recent impact, such that the volatile ice underneath is exposed. Such behaviour is well-known in our own solar system, see the 3rd figure at this link.

Clearly, until we observe more interstellar objects, we can't say whether 'Oumuamua is unusual or not in its properties.

 

[Klystron]

We've never seen an interstellar object before, and don't know much of the history of 'Oumuamua, i.e: How old is is?; How long is it since it was ejected from its parent star (if it had one)?; Has it passed through any dust clouds before entering the solar system?; How many other solar systems has it passed through?

If a comet had traveled for considerable periods of time in interstellar space, it is entirely possible that the volatiles were heavily depleted by interactions with radiation, such as sputtering or by sublimation earlier in its history. Alternatively, the comet may be covered with a thick layer of dust. The age of craters in our own solar system is broadly correlated with the age of the crater in question, so it is to be expected that an old object may be covered in a lot of dust. Thus, the varying brightness may be related to a more recent impact, such that the volatile ice underneath is exposed. Such behaviour is well-known in our own solar system, see the 3rd figure at this link.

Clearly, until we observe more interstellar objects, we can't say whether 'Oumuamua is unusual or not in its properties.

Least Hypothesis: space object until data review shows artifact. Does every variable star indicate a partial Dyson construct?

 

[DrStupid]

Especially if only one side of the object retained volatiles to off-gas? Such that the coma dwindled down each time the snowy side swung into shadow ??

Do you mean that the coma grows and shrinks in the extend as measured for the brightness? As the shape of the curve is quite symmetric this would require a steady state where the gas escapes almost as fast into space at it is delivered by evaporation from the surface. That would result in a large amount of released gas and finally in a tail. But we cannot see a tail or any gas or dust near the object.

 

[DrStupid]

If a comet had traveled for considerable periods of time in interstellar space, it is entirely possible that the volatiles were heavily depleted by interactions with radiation, such as sputtering or by sublimation earlier in its history. Alternatively, the comet may be covered with a thick layer of dust. The age of craters in our own solar system is broadly correlated with the age of the crater in question, so it is to be expected that an old object may be covered in a lot of dust. Thus, the varying brightness may be related to a more recent impact, such that the volatile ice underneath is exposed. Such behaviour is well-known in our own solar system, see the 3rd figure at this link.

That doesn't fit to TEFLing's assumption in #51 which my reply referred to.

 

[TEFLing]

Do you mean that the coma grows and shrinks in the extend as measured for the brightness? As the shape of the curve is quite symmetric this would require a steady state where the gas escapes almost as fast into space at it is delivered by evaporation from the surface. That would result in a large amount of released gas and finally in a tail. But we cannot see a tail or any gas or dust near the object.

The light curves are widely available, not sure I would characterize them as symmetric

Rather they evidence a lot of rapid fluctuations, especially on the brightening side of the curve

A small object, producing on again off again emissions, might generate such a curve... The coma would be so diffuse as to be unobservable far from the object

 

[metiman]

The idea that this object may have been manufactured is fundamentally different from any supernatural explanations. Supernaturalism is itself entirely absurd and without evidence and what's more lacks even explanatory value.

This object is the first in human history to not be plausibally explained be ANY theory. In fact the only thing we know for certain about it is that we have not seen anything like it before. It does not present like an asteroid due to the acceleration and albedo and if the albedo is explained by a freakishly unlikely shape that just makes it even more difficult to explain away. And if it is a comet it certainly does not look like any comet we have ever seen. We have no evidence that a comet can present like this object.

So what can science tell us about this object? Very little really except that we must accept that we lack sufficient data to say anything conclusively about what it is or is not. We simply do not know and will not know unless we chase after it or it turns around or we discover that it left behind some further uh natural objects.

Science is not magic. It is just the best way our species has yet discovered to learn about the world around us. We must not let it blind us to what may be true even if we cannot prove it. We must remain open to the possible. There is no evidence so far that conflicts with the idea that Oumuamua is artificial. It probably isn't but that does not mean that we know that it isnt. We absolutely cannot and should not rule out the possibility.

What concerns me is that our near religious devotion to the scientific method and perhaps the fear of any working scientist of being labeled as a crank for even considering the possibility of artificial origin may prevent us from doing what really makes sense here.

In the name of science we are behaving like short sighted fools. Of course we should be chasing this thing down. We have the ability. We just need to come together as a species and pay for it. Nothing like this has ever happened before. We have never before had a compelling reason to actually go out there.

Well we do now, but only if people allow themselves to be open minded about what is possible and not just dismiss it as another asteroid or comet when such explanations are entirely without evidence and as far as believing something only because you want it to be true isn't that what dismissing an artificial origin is all about? Saying anything conclusive about what Oumuamua is not is not science.

What we do have evidence for is that this is one of the strangest and most compelling objects we have ever seen in space and that we most definitely cannot rule out an artificial origin. And without evidence we absolutely must not because what if it really is artificial and we just let it leave our system without even trying to take a closer look? We like to think of ouselves as curious and explorative, but are we?

 

[jim mcnamara]

Moved to General Discussion.