Evidence for ET?

[popeyespappy]

The answer to that is velocity. Nothing in this solar system except the sun could have accelerated Oumuamua to the speed it was moving when it was detected. The trajectory was wrong for it to have been accelerated by our star. It came from the direction of Vega, that doesn't mean it originated there, and is now headed in the direction of Pegasus.

It is on a hyperbolic orbit, which, per Newtonian mechanics, should be completely predictable.  Why the deviation from the hyperbola?

Sorry. I was answering a different question. Apparently one that wasn't asked.

[Jehanne]

That's possible; it's a question of F = ma.

Again, comets frequently show major deviations from keplarian orbits due to jetting effects of volatile sublimation.   Why are we so surprised this object should do the same thing just because it came in from outside the solar system?

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That is the question.

Impact with another object is ridiculously improbable and would have produced debris. It's also been accelerating over a fair bit of time rather than a one-off bump.

Outgassing of volatiles wasn't observed. It may be too distant to make out the gasses, though that seems unlikely.

Both of the above should have altered the rate of its tumble, but that wasn't observed either.

It's possible that it's a light sail or fragment of a light sail, though the reddish colour makes that unlikely. The better answer is our old stand-by, "We don't know." It has made Oumuamua a bit more interesting though. Regardless of what it is, it's unlikely that our first detection of a large extra-solar object is wildy anomalous, so we'll likely be visiting something similar with a probe in the next decade or two.

Thrust of outgassing would not appreciably effect the rate of tumble if the thrust vector directs through the elongated object near the middle.  Since the expelled gas is not attached to the object, the departure of the gas would also have no effect on the angular momentum of the remaining mass of the object.

It would be interesting to determine how much density and optical depth would the plume of expelled gas need to have to be detectable from earth, and how large must the plume be to be resolvable separately from object itself as a coma.   Couple that with reasonable estimate of the velocity of the outgas would put a constaint on the amount of material that can be outgased without being detected from earth.  That in turn would provide a constraint on the maximum amount of orbital energy change outgassing can cause without the outgas being detectable from earth.

A solar sail able to appreciably affect the orbit of a solid object of reasonable density a good fraction of a km long would be enormous and at least severa Times larger in dimension than the object itself.   Unless the sail is a near perfect, non-scattering mirror reflector from IR to UV, we would have been able to detect the sail more easily than the object itself???

Extraordinary claims require extraordinary evidence (of course!), but, when does an artificial, albeit, natural, explanation become the most probable?

[Anomalocaris]

What’s less improbable? Undetected outgassing, knowing from experience most primitive small objects from distant parts of the solar system will outgas when heated by the sun for the first time, or undetected solar sail?

[onlinebiker]

ET - Eddie Torres - The Extra-Testicle....






( for the Cheech and Chong fans)

[Paleophyte]

That is the question.

Impact with another object is ridiculously improbable and would have produced debris. It's also been accelerating over a fair bit of time rather than a one-off bump.

Outgassing of volatiles wasn't observed. It may be too distant to make out the gasses, though that seems unlikely.

Both of the above should have altered the rate of its tumble, but that wasn't observed either.

It's possible that it's a light sail or fragment of a light sail, though the reddish colour makes that unlikely. The better answer is our old stand-by, "We don't know." It has made Oumuamua a bit more interesting though. Regardless of what it is, it's unlikely that our first detection of a large extra-solar object is wildy anomalous, so we'll likely be visiting something similar with a probe in the next decade or two.

Thrust of outgassing would not appreciably effect the rate of tumble if the thrust vector directs through the elongated object near the middle.  Since the expelled gas is not attached to the object, the departure of the gas would also have no effect on the angular momentum of the remaining mass of the object.

It would be interesting to determine how much density and optical depth would the plume of expelled gas need to have to be detectable from earth, and how large must the plume be to be resolvable separately from object itself as a coma.   Couple that with reasonable estimate of the velocity of the outgas would put a constaint on the amount of material that can be outgased without being detected from earth.  That in turn would provide a constraint on the maximum amount of orbital energy change outgassing can cause without the outgas being detectable from earth.

A solar sail able to appreciably affect the orbit of a solid object of reasonable density a good fraction of a km long would be enormous and at least severa Times larger in dimension than the object itself.   Unless the sail is a near perfect, non-scattering mirror reflector from IR to UV, we would have been able to detect the sail more easily than the object itself???

The thrust vector is unlikely to be that close to axial all the time. There should have been some evolution of the tumble if outgassing had been significant enough to produce linear acceleration.

I suspect the answer to how much gas could be expelled without being detected gets complicated pretty quickly. I'll vary considerably depending on the molecules involved and their tendency to fluoresce. Even if the gas weren't directly visible from earth as a coma or tail its presence should have modified the spectral absorption lines. That wasn't observed either.

We don't actually know the size of the object. It's just a point of light in our most powerful telescopes. The dimensions were inferred from the light curve, distance, and some assumptions about the albedo and density. Assuming an albedo of about 0.1, similar to outer solar system objects, you get an asteroid ~1000 m long and ~200 m wide. If it's a light sail then you'd hope it's designed with a much higher albedo (~1) and likely isn't pushing anything other than its own miniscule mass. That gives you dimensions closer to ~300 m by ~80 m and a tenth of a millimeter thick. That implies that it's folded up a bit too, possibly damaged or discarded. If it were a flat sheet then the light curve would plunge to near zero as it tumbled edge on to us.

I don't think that it is a light sail. The colour and shape are wrong for a start. More likely some mundane explanation. Still, I'd very much like to go and check it out.

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Here's the original paper (PDF Download) along with a less technical article in Scientific American. And here's a rebuttal.

TL;DR Oumuamua is weird and we don't know why.

[Anomalocaris]

The thrust vector needn’t be close to axial.  It just need to be close to the instantaneous center of rotation so it dies’t impart a significant torque while imparting the thrust.    It can squirt in all sorts of directions and impart translation along multiple axis at different times without effecting the tumbling.

A functionally navigating light sail should not exhibit any sort of light curve that suggest tumbling, because it would need to be stabilized and accurately pointed relative to the star to achieve desired efficiency and control.

If The suggestion is it is an uncontrolled and tumbling light sail, I can think of another way to try to corroborate such a scenario. A light sail ought to be very flimsy and low mass. So it should have very low thermal inertia. So as it tumbled and presents changing aspect to the sun, it’s infrared signature should show almost no latency compare to variations in the amount of sunlight it receives. Is that the case?

[ignoramus]

This guy makes sense ...

[Jehanne]

It's a great video and first-rate analysis. Still, the anomalous deviation on its hyperbolic orbit cries out for an explanation.

[Anomalocaris]

Outgassing?

[Angrboda]

It's a great video and first-rate analysis.  Still, the anomalous deviation on its hyperbolic orbit cries out for an explanation.

I'm sick of all this crying. I'm turning a deaf ear to their cries and simply not coming to any conclusion.