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 ...
For an interesting, entertaining read skip to the Summary and Conclusions part at the end. Wow.
Bruce
Re: 'Oumuamua an ETI lightsail?
Posted: Tue Nov 06, 2018 11:32 am
by JohnD
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
Re: 'Oumuamua an ETI lightsail?
Posted: Wed Nov 07, 2018 12:24 am
by BDanielMayfield
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.
Bruce
Re: 'Oumuamua an ETI lightsail?
Posted: Wed Nov 07, 2018 9:03 am
by JohnD
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
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.
<<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.>>
