‘Oumuamua, Thin Films and Lightsails

Post by dang » Tue, Oct 30, 2018, 9:31 PM UTC

stephengillie wrote: post #40

d_burfoot wrote: post #39

Paging Elon Musk, Jeff Bezos, et al: the next time one of these objects appears, we should try to capture it somehow, or at least divert its trajectory enough that it stays in the solar system and we can study it further. Nabbing one of these things would be a spectacular achievement, comparable to the moon landings, and would likely be of significant scientific value.

Musk missed, and his car is headed for the asteroid belt instead of Mars.

Post by Qwertystop » Tue, Oct 30, 2018, 9:51 PM UTC

mannykannot wrote: post #55

Tossrock wrote: post #18

Given Oumuamua's well documented non-gravitational acceleration, what was the cause? That's the key question this article – and the paper it cites – are investigating. Comet-like off-gassing has been mostly ruled out due to the lack of observed dust or gas around the object, as well as lack of effect on spin. The paper suggests that a highly reflective 0.3mm-thick film 20m in diameter could be consistent with the obs…

Assuming a uniform thickness and density, is the acceleration of a light sail not independent of area? I get the impression that the radius given is an upper limit based on the apparent magnitude and assuming a high albedo. The light curve indicates that the object is tumbling, so a thin sheet would rarely (if ever) be oriented approximately optimally to act as a sail. I have not figured out how the authors have take…

Post by bottled_poe » Tue, Oct 30, 2018, 10:23 PM UTC

abecedarius wrote: post #34

Tossrock wrote: post #18

Given Oumuamua's well documented non-gravitational acceleration, what was the cause? That's the key question this article – and the paper it cites – are investigating. Comet-like off-gassing has been mostly ruled out due to the lack of observed dust or gas around the object, as well as lack of effect on spin. The paper suggests that a highly reflective 0.3mm-thick film 20m in diameter could be consistent with the obs…

It’s a fascinating mystery, but I gotta say that’d make a crappy lightsail, considering that even at our current tech level we could make a much lighter one if we could manufacture it in space. (The experiments that have flown were all constrained to survive launch and unfolding.)

Post by gwern » Tue, Oct 30, 2018, 10:33 PM UTC

skykooler wrote: post #50

gwern wrote: post #46

Earlier quoted context omitted.

Fermi's paradox demonstrates it's almost certainly not a light sail. For it to be a light sail which was observed by chance by our totally unprepared observatories after a window of less than a century but also consistent with all our observations of the universe, we would need to hypothesize that we got extraordinarily lucky to observe a super-rare artifact, or that countless (or one vast) interstellar, pan-galactic…

Or that this was a relatively nearby civilization, and the light sail was intentionally headed toward our solar system (like a few of our proposed interstellar missions to Alpha Centauri).

Post by gwern » Tue, Oct 30, 2018, 10:37 PM UTC

modzu wrote: post #56

gwern wrote: post #46

Earlier quoted context omitted.

Fermi's paradox demonstrates it's almost certainly not a light sail. For it to be a light sail which was observed by chance by our totally unprepared observatories after a window of less than a century but also consistent with all our observations of the universe, we would need to hypothesize that we got extraordinarily lucky to observe a super-rare artifact, or that countless (or one vast) interstellar, pan-galactic…

thats not true. if the probability of whether or not its a sail could be calculated, it would have been in the paper ;)