15 Oct '15 17:37>
http://www.zmescience.com/space/alien-megastructure-star-aliens-
Probably.
Probably.
Originally posted by avalanchethecatWhat is puzzling is the odd timing of the reduction of light intensity. 800 days, down what, 13%, 1200 days later down 22% or something like that. THAT is what has them flustrated.
http://www.zmescience.com/space/alien-megastructure-star-aliens-
Probably.
Originally posted by DeepThoughtThe article I read said it was not a young star, young stars can change intensity levels quite a bit but old stars like Sol have settled down to a stable output, more or less.
The article doesn't say what kind of star it is. The article talks about it as if it's a young star, if it's very young I wouldn't be that surprised about luminosity fluctuations, but the researchers are, so simple explanations seem to be ruled out. I don't see the problem with improbable explanations - there must be quite a few stars in a sphere 500 p ...[text shortened]... ig enough to block out 20 odd percent of a stars light is stable against gravitational collapse.
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Now let’s have a care here. The paper doesn’t mention aliens, and it doesn’t even imply aliens. Not directly, at least. But the astronomers found a star so odd, with behavior so difficult to explain, that it’s clear something weird is happening there. And some of the astronomers who did the work are now looking into the idea that what they’ve found might (might!) be due to aliens.
But don’t let this idea run away with you (as it has with some folks on social media and, no doubt, will in some sketchier “media” outlets any minute now). The scientists involved are being very skeptical and approaching this the right way: more of an interested “Hey, why not?” follow-up, as opposed to the Hollywood renegade astronomer who just knows it’s aliens but (fist shaking in the air) just can’t convince those uptight Big Astro sellouts!
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The authors of the paper went to some trouble to eliminate obvious causes. It’s not something in the telescope or the processing; the dips are real. It’s not due to starspots (like sunspots, but on another star). My first thought was some sort of planetary collision, like the impact that created the Moon out of the Earth billions of years ago; that would create a lot of debris and dust clouds. These chunks and clouds orbiting the star would then cause a series of transits that could reproduce what’s seen.
The problem with that is that there’s no excess of infrared light from the star. Dust created in such impacts warms up and glows in the IR. We know how much IR stars like KIC 8462852 give off, and we see just the right amount from it, no more. The lack of that glow means no (or very little) dust.
The last idea the astronomers looked at was a series of comets orbiting the star. These could be surrounded by clouds of gas and other material that could produce the dips seen. The lack of IR is puzzling in that case, but not too damning. If another star happened to pass nearby, then its gravity could disturb the first star’s Oort cloud, the region billions of kilometers out where we think most (if not all) stars have billions of icy objects. This disturbance could send these ice chunks flying down toward the star, where they could break up, creating all those weird dips—ices in them would heat up, blow off as a gas, and could explain the odd shapes of the dips detected, too.
And, as it happens, there is another star pretty close to KIC 8462852; a small red dwarf about 130 billion kilometers out. That’s close enough to affect the Oort cloud.
This doesn’t close the case, though. Comets are a good guess, but it’s hard to imagine a scenario where they could completely block 22 percent of the light from a star; that’s a huge amount. Really huge. .....
Originally posted by DeepThought
The article doesn't say what kind of star it is. The article talks about it as if it's a young star, if it's very young I wouldn't be that surprised about luminosity fluctuations, but the researchers are, so simple explanations seem to be ruled out. I don't see the problem with improbable explanations - there must be quite a few stars in a sphere 500 p ...[text shortened]... ig enough to block out 20 odd percent of a stars light is stable against gravitational collapse.
Nothing big enough to block out 20 odd percent of a stars light is stable against gravitational collapse
Originally posted by googlefudgeA sphere won't work. They have to all be in orbits and if the orbits overlap they'll start to collide. You could have some ring like structure - we know this is stable because of Saturn's rings - but even then collisions would be a major problem. Further the light from the star fluctuates, which implies an uneven distribution. Why would they build an asymmetrical structure? If it's a sphere of objects orbiting the star the way a planet would then if the objects are not connected to each other they would definitely be unstable against collapse. If they are connected to each other and the whole thing is planet sized then they'd have to be proof against collisions at speeds of the order of 10 km/s. I don't think it's something any sane species would do. You may as well just cover one of the dead planets in your system with solar cells.Nothing big enough to block out 20 odd percent of a stars light is stable against gravitational collapse
Based on what assumptions?
A Dyson Sphere is [based on current knowledge] impossible, but what he was really
thinking of is a huge spherical array of independently orbiting solar energy collectors.
Such collectors [ultra thin ...[text shortened]... not impossible, you are far to quick to rule this impossible without
having thought about it.
Originally posted by DeepThoughtA sphere would work if you could get materials strong enough to hold together, the whole assembly would presumably have to spin to at least lessen the stresses in the equatorial region but it would have to be strong enough to support the rest of the sphere.
A sphere won't work. They have to all be in orbits and if the orbits overlap they'll start to collide. You could have some ring like structure - we know this is stable because of Saturn's rings - but even then collisions would be a major problem. Further the light from the star fluctuates, which implies an uneven distribution. Why would they build an ...[text shortened]... s would do. You may as well just cover one of the dead planets in your system with solar cells.
Originally posted by DeepThoughtOr alternatively you have a spherical cloud of objects around 1 Au out ~1million km thick
A sphere won't work. They have to all be in orbits and if the orbits overlap they'll start to collide. You could have some ring like structure - we know this is stable because of Saturn's rings - but even then collisions would be a major problem. Further the light from the star fluctuates, which implies an uneven distribution. Why would they build an ...[text shortened]... s would do. You may as well just cover one of the dead planets in your system with solar cells.
Originally posted by googlefudgeCan you calculate the best size for a Dyson sphere? You can see if too close to the sun the energy would be to intense and if too far too dilute, so what would be the best size?
Or alternatively you have a spherical cloud of objects around 1 Au out ~1million km thick
with the mirrors in non-intersecting orbits.
Bang, Dyson Sphere.
https://en.wikipedia.org/wiki/Dyson_sphere
http://io9.com/5902205/how-to-build-a-dyson-sphere-in-five-relatively-easy-steps
von Neumann probes and Dyson spheres: what exploratory engineer ...[text shortened]... us about the Fermi paradox
https://www.youtube.com/watch?feature=player_embedded&v=zQTfuI-9jIo
Originally posted by sonhouseYou do realise that there is no restoring force if the sphere gets displaced relative to the star don't you? A body inside a hollow shell of matter feels no net gravitational forces from the shell, and similarly the shell feels no net force from the contained object. This means that your star can drift from the central point of the sphere. It's not unstable, in the sense that the rate of displacement won't increase after the perturbation, but it won't decrease either. This is something you'll have to fight against. Worse, if there is any transient asymmetry in the solar wind you'll get a driven displacement that could be very hard to control as the star can push harder than you can, being the source of almost all energy in the system. You also have to clear a huge volume of space of comets and so forth.
Can you calculate the best size for a Dyson sphere? You can see if too close to the sun the energy would be to intense and if too far too dilute, so what would be the best size?
Originally posted by DeepThought
This objection does not apply to googlefudge's swarm sphere. The problem I have with that is that the vast number of objects you need are all in independent orbits and will interact. You might be able to avoid actual collisions without too much grief, but you will have swarm elements thrown inwards towards the star and out into space because they inter ...[text shortened]... ify more plausible mechanisms, so personally I think alien megastructures are ruled out as well.
This objection does not apply to googlefudge's swarm sphere. The problem I have with that is that the vast number of objects you need are all in independent orbits and will interact. You might be able to avoid actual collisions without too much grief, but you will have swarm elements thrown inwards towards the star and out into space because they interact.
Also you need to have enough solar cells to make this possible and they use rare earths. Focus for a second on the word rare. Where are you going to get enough stuff to make your solar cells from, building the sphere is a bit of a waste of effort if you can't cover the entire interior with solar energy collectors.
But the real giveaway that this effect (returning to the star in the OP) is not due to aliens is that a Dyson sphere would still have to emit copious amounts of waste heat. So we should see infra-red and there isn't enough to justify more plausible mechanisms, so personally I think alien megastructures are ruled out as well.
Originally posted by googlefudgeThe bit about giving off IR could be countered by IR reflective surfaces, effectively hiding all IR. We are getting pretty advanced in stealth technology and I would think a problem like that would be turned into an advantage, using the IR as an extra energy source. The outside could look like the cosmic background, 3 odd degrees K.
[quote]This objection does not apply to googlefudge's swarm sphere. The problem I have with that is that the vast number of objects you need are all in independent orbits and will interact. You might be able to avoid actual collisions without too much grief, but you will have swarm elements thrown inwards towards the star and out into space because the ...[text shortened]... totally non-viable with objections that are trivial to counter.
That's bias, not skepticism.
Originally posted by DeepThoughtI did not know that. Interesting. Does it apply to a ring too?
A body inside a hollow shell of matter feels no net gravitational forces from the shell, and similarly the shell feels no net force from the contained object.