'Oumuamua an ETI lightsail?

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BDanielMayfield
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'Oumuamua an ETI lightsail?

Post by BDanielMayfield » Thu Nov 01, 2018 2:26 am

The guys at Centauri Dreams are stoked by a paper proposing that 'Oumuamua was could have been a lightsail probe or a piece of one. See: https://www.centauri-dreams.org/2018/10 ... lightsails

I don't have an opinion on this one, except that I have previously stated with strong confidence that it was a natural interstellar object. But I could be wrong ...

No, wait, nah.

But then again, just maybe ...


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Last edited by BDanielMayfield on Thu Nov 01, 2018 3:02 am, edited 1 time in total.
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BDanielMayfield
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Re: 'Oumuamua an ETI lightsail?

Post by BDanielMayfield » Thu Nov 01, 2018 2:53 am

Here's the paper being discussed: https://arxiv.org/pdf/1810.11490.pdf

For an interesting, entertaining read skip to the Summary and Conclusions part at the end. Wow.


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Re: 'Oumuamua an ETI lightsail?

Post by JohnD » Tue Nov 06, 2018 11:32 am

I can't criticise their calculations, but note the speculation, supported by Loeb, that this was "debris from an advanced technological equipment". But their calculations are based the observed non-gravitational acceleration of Oumuamua.

How would a debris light sail behave on entry to and exit from a solar system? It would have a random alignment with the star's radiation. Would it tumble, like an unguided orbital object on re-entry to the atmosphere? Or would it self-align, like a sphere-cone aeroshell?


In that case, wouldn't it self-align as it came in, producing observable deceleration at that stage? If it accelerated on exit, then it must have either self aligned then - how likely? - or as the authors suggest as "more exotic", it was actually under guidance. They point out Do et al's estimate of an unreasonable number of Oumumamua objects if they were natural.
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Re: 'Oumuamua an ETI lightsail?

Post by BDanielMayfield » Wed Nov 07, 2018 12:24 am

JohnD wrote:
Tue Nov 06, 2018 11:32 am
I can't criticise their calculations, but note the speculation, supported by Loeb, that this was "debris from an advanced technological equipment". But their calculations are based the observed non-gravitational acceleration of Oumuamua.

How would a debris light sail behave on entry to and exit from a solar system? It would have a random alignment with the star's radiation. Would it tumble, like an unguided orbital object on re-entry to the atmosphere? Or would it self-align, like a sphere-cone aeroshell?

In that case, wouldn't it self-align as it came in, producing observable deceleration at that stage? If it accelerated on exit, then it must have either self aligned then - how likely? - or as the authors suggest as "more exotic", it was actually under guidance. They point out Do et al's estimate of an unreasonable number of Oumumamua objects if they were natural.
JOhn
Tumbling motion is what 'Oumumamua was observed to have, so the notion that it is or was a still functioning artifact seems wildly speculative. A bit less wild is the idea that it was/is a bit of some other civilization's old space junk that's just drifting between the stars.

Unfortunately we never noticed this object until it was already on the way out of our system, so anything it may have done before we noticed it is unknowable.

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Re: 'Oumuamua an ETI lightsail?

Post by JohnD » Wed Nov 07, 2018 9:03 am

Thanks, Bruce, and thanks for making the point that we didn't see Oumuamua on its way in, so no observations.

Fascinating idea, though, and one that highlights that the images of O. as a long piece of rock are almost as speculative!
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Lightsail built like a brick...

Post by neufer » Wed Nov 07, 2018 2:08 pm

Art Neuendorffer

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Re: 'Oumuamua an ETI lightsail?

Post by Chris Peterson » Wed Nov 07, 2018 2:43 pm

JohnD wrote:
Wed Nov 07, 2018 9:03 am
Thanks, Bruce, and thanks for making the point that we didn't see Oumuamua on its way in, so no observations.

Fascinating idea, though, and one that highlights that the images of O. as a long piece of rock are almost as speculative!
John
But we already know of asteroids within our system with similar aspect ratios.

The paper describes what is possible, but what we should be most concerned with is what is plausible. And it isn't a space probe!
Chris

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Re: 'Oumuamua an ETI lightsail?

Post by JohnD » Wed Nov 07, 2018 3:16 pm

What about this "non-gravitational" acceleration, then Chris?
Is out-gassing sufficient explanation?
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Re: 'Oumuamua an ETI lightsail?

Post by Chris Peterson » Wed Nov 07, 2018 3:20 pm

JohnD wrote:
Wed Nov 07, 2018 3:16 pm
What about this "non-gravitational" acceleration, then Chris?
Is out-gassing sufficient explanation?
It appears to be so. Again, it's reasonable to ask what is more plausible- outgassing or some kind of alien probe.
Chris

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Re: 'Oumuamua an ETI lightsail?

Post by BDanielMayfield » Wed Nov 07, 2018 5:11 pm

Chris Peterson wrote:
Wed Nov 07, 2018 3:20 pm
JohnD wrote:
Wed Nov 07, 2018 3:16 pm
What about this "non-gravitational" acceleration, then Chris?
Is out-gassing sufficient explanation?
It appears to be so. Again, it's reasonable to ask what is more plausible- outgassing or some kind of alien probe.
Wise to go with the most plausible explanation. And, to consider the source. The people most into this ET explanation are also the most into trying to turn interstellar flights of fancy (SF) into reality.

I only started this thread because I thought it would make for interesting conversation. I didn't add this to the previous threads dealing with 'Oumuamua because even I felt it was a little too "out there". But still, I try to be open minded enough to leave the door open to interesting possibilities.

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Re: 'Oumuamua an ETI lightsail?

Post by bystander » Thu Nov 08, 2018 6:20 pm

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alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: 'Oumuamua an ETI lightsail?

Post by neufer » Thu Nov 08, 2018 6:42 pm

https://en.wikipedia.org/wiki/Phantom_Zone wrote:
Click to play embedded YouTube video.
<<The Phantom Zone is a fictional prison dimension appearing in American comic books published by DC Comics, commonly in association with stories featuring Superman. It first appeared in Adventure Comics #283 (April 1961), and was created by Robert Bernstein and George Papp. The Phantom Zone was a "pocket universe" discovered by Jor-El that existed outside the space-time continuum; used on the planet Krypton as a humane method of imprisoning criminals. The inmates of the Phantom Zone reside in a ghost-like state of existence from which they can observe, but cannot interact with, the regular universe. Inmates do not age or require sustenance in the Phantom Zone; furthermore, they are telepathic and mutually insubstantial. As such, they were able to survive the destruction of Krypton and focus their attention on Earth, as most of the surviving Kryptonians now reside there. Most have a particular grudge against Superman because his father created the method of their damnation, and was often the prosecutor at their trials.>>
Art Neuendorffer