‘Oumuamua, Thin Films and Lightsails
centauri-dreams.org
centauri-dreams.org
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 observed acceleration. This also happens to be similar in dimensions to lightsails that we've proposed (and in a few cases deployed) here on/around Earth.
Of course, it's just one hypothesis. Could the acceleration be due to some other effect, like the Pioneer anomaly? Sure. Unfortunately, there's no way to ever confirm it given that the object is beyond our ability to observe or catch. But it's still very interesting speculation.
say you instead make the space craft tumble but make the sails able to change their albedo (how reflective they are). If you wanted to make a course correction, you'd alternate how reflective they were. If you wanted a push away from a sun, you'd make the side facing a sun bright. If you wanted to fall in more towards a sun, you'd make the side facing a sun dark. Would that work?
How much do light sails depend on brightness (light pressure) vs just absorbing molecules in the Solar wind?
Edit: Wikipedia says light pressure from photons is most of the effect, but still I can't figure out the difference between a black body sail and a reflective sail.
And also, maybe some of the stored and emitted heat can be directed somehow.
Something of that size (area) and weight doesn't seem like some kind of naturally occurring object though.
Even if it is a piece of debris, that is super, super interesting.
Eh, who am I kidding, even if it was produced through some natural process, that is still interesting.
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 taken this into account in their calculation - could it be as simple as halving the area to give an effective value?
This is a new one on me, I'm not aware of any rigorous lower limits on off gassing which have actually ruled it out as the source of the acceleration. Do you have any citations?
Perhaps the main ship is on the way!
Solar sails to be effective would have to be much larger than the craft itself, and also very reflective (by definition), though the reflection don't have to omnidirectional (stealth aircraft/ship principle -- make it reflect a lot but only in very specific direction so that it seems dark to most observers).
Given this, the craft would most likely PRECEDE the sail but would also be smaller and darker and we would most likely not be able to spot it.
But anyway, if you carry a solar sail to accelerate, why would you not use the same sail to decelerate as much as possible too?
> In fact, the strong correlation between ʻOumuamua's velocity and the local standard of rest might mean that it has circulated the Milky Way several times and thus may have originated from an entirely different part of the galaxy.
By contrast when we have ships moving regularly between Earth, Mars, the Moon, and wherever else - we'll have much more infrastructure and technological development enabling us to have a much better chance of being able to rapidly react to the next 'weird thing' we see in space. And seeing how many weird things we're already starting to observe now that we've just barely begun to be able to open our eyes, I expect this is just the beginning. Consider we still lack the technology to determine whether or not there is some giant super-earth floating around in our own solar system. Sometimes in space it's much easier to see things billions of light years away than it it is to see something right next door.
Devil's advocate would raise the example of Dune perhaps, with a fairly decent IMO SyFy network TV miniseries, a lot more nuanced than the film and far more from the novel but didn't have the staying power of either of the two film versions. (Not that any of the film versions or the miniseries seems to be broadly loved)
As far as I can see, the observed hyperbolic trajectory doesn't seem consistent with a scenario where the target of the sail's payload would be our solar system.
I'm fairly certain we can't detect that yet even if they had.
How good is our aim across 4.4 light years?
Genuine question, this is well outside my wheelhouse.
("Is the interstellar object Oumuamua a lightsail from an alien civilization? " at the time of this comment)
All: Accounts that do that eventually lose submission privileges on HN, so please don't!
;)
So in other words, the probability is not Zero. Meaning it is very much worth considering and this article is legit.
That same probability applies to the light sail.
On the other hand, we have essentially no knowledge about what can possibly be flying around out there and thus your claim that it is extremely unlikely to be an artificial object is not based on anything but your own conviction that this is the case.
Probability allows you to say something with confidence if you have information to work out the probability. If you have no information then you have no probability.
I think that our knowledge of the universe does allow me to conclude with some degree of certitude that it is highly unlikely to find a whale on an extra-solar trajectory.
On the other hand, we know nothing about the sort of objects that could exist out there and about the possibility of alien civilisations.
I am not saying that it is likely or unlikely to be a light sail because the fact is that we don't know enough to assign a likelihood. That's as unbiased as can be.
I'm having trouble finding it at the moment, but somewhere out there is a pretty good article that points out that even though more people are now carrying cameras than ever before, UFO sightings have basically fallen off a cliff. They rose with the advent of jet aircraft and the space age, and then fell away in the era of drones. (The ones that I found in search results weren't the one I was thinking of.)
"Lightsail" is being floated as a possible explanation for this because we've recently imagined that technology. A few decades earlier, and nobody would imagine it as an explanation; a few decades later, and we'll have some other favorite new possible explanation that we can't imagine now.
The article wasn't terrible, though.
Or to put it another way, humans conceptualize, observe and measure based on what they currently know and the tools they have.
My point again is we all to often fill the vacuum of what we don't know with 'the extent of our knowledge and experience is the extent of the entire universe'.
We have no idea about what we don't know...
Note that the title on that article is actually "‘Oumuamua, Thin Films and Lightsails". I suppose it might have been different when submitter submitted it, but that seems unlikely.
https://en.wikipedia.org/wiki/Betteridge%27s_law_of_headline...
Doing that to titles is explicitly against the HN guidelines and eventually will cause an account to lose submission privileges.
Why was this changed in the HN submission? It sounds much more click-baity than it is.