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  1. Standard member avalanchethecat
    Not actually a cat
    15 Oct '15 17:37
    http://www.zmescience.com/space/alien-megastructure-star-aliens-

    Probably.
  2. Standard member sonhouse
    Fast and Curious
    15 Oct '15 19:08 / 1 edit
    Originally posted by avalanchethecat
    http://www.zmescience.com/space/alien-megastructure-star-aliens-

    Probably.
    What 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.

    I don't even see why that would happen if you had a civilization so advanced it could gather a good portion of the entire star's solar output.

    The only thing I can think of is, supposing it IS an advanced civilization, is a large portion of the equatorial region of the star covered with solar cells, but they are not in a circular orbit which would cause the rise and fall in intensity in a more regular manner, but maybe the solar installation is in some kind of elliptical orbit and we are viewing it kind of at an angle where the assembly partially blocks the light from that star but at strange intervals. If there is a pattern, maybe it will take a hundred years of observation to suss out.

    Then again, it could just be an extreme variable star with a god awful sense of timing

    Can you imagine, a hundred, two hundred years from now they prove it is an actual very powerful alien civilization and they decide to send a spacecraft there, say at 99.99999 % of c. So 1400 years passes on Earth, the crew ages say 3 years, they get there and the folks there give them REALLY advanced science stuff. So they hop back to Earth, now close to 3000 years has gone by, and they get back only 6 or 7 years older (the crew) only to find out Earth science has advanced to equal or surpass the people around that star.... There has to be a story in there somewhere.
  3. Standard member DeepThought
    Losing the Thread
    16 Oct '15 11:41
    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 parsecs across - so it depends on how unlikely a freakish configuration is. One thing it is not is due to is the activities of aliens. Nothing big enough to block out 20 odd percent of a stars light is stable against gravitational collapse.
  4. Standard member sonhouse
    Fast and Curious
    16 Oct '15 11:53
    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.
    The 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.
  5. 16 Oct '15 11:59
    http://www.slate.com/blogs/bad_astronomy/2015/10/14/weird_star_strange_dips_in_brightness_are_a_bit_baffling.html

    ......
    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!


    ........
    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. .....
  6. 16 Oct '15 12:05
    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


    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 mirrors] could easily reach planet size without gravitational
    collapse.

    And if enough of them pass in front of the star at one time, then you can get any amount
    of blocking you like.

    Such a structure under construction could produce the observed data.

    It's highly unlikely but it's not impossible, you are far to quick to rule this impossible without
    having thought about it.
  7. Standard member DeepThought
    Losing the Thread
    16 Oct '15 12:59
    Originally posted by googlefudge
    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.
    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 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.
  8. Standard member sonhouse
    Fast and Curious
    16 Oct '15 13:40 / 1 edit
    Originally posted by DeepThought
    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.
    A 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.

    Quite the construction project, eh. A sphere say 100 million km radius or so. Easy peasy
  9. 16 Oct '15 13:51
    Originally posted by DeepThought
    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.
    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 engineering can tell us about the Fermi paradox
    https://www.youtube.com/watch?feature=player_embedded&v=zQTfuI-9jIo
  10. Standard member avalanchethecat
    Not actually a cat
    16 Oct '15 17:08
    Vast swarms of hostile replicators.
  11. Standard member sonhouse
    Fast and Curious
    17 Oct '15 07:33
    Originally posted by googlefudge
    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
    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?
  12. Standard member DeepThought
    Losing the Thread
    17 Oct '15 09:18
    Originally posted by sonhouse
    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?
    You 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.

    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.
  13. 17 Oct '15 12:26
    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.


    You can use solar sails [and the literally astronomical amount of energy at your disposal] to make the
    minor course corrections needed. For a civilisation capable of building such a structure, this is a trivial
    problem.

    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.


    Actually this is not a problem either.

    If you look at the links I suggested this issue is dealt with.

    Most of the structure is concentration mirrors, which can be made from non-rare materials.

    The power converters which are much much smaller and have much less net mass can then be made from
    the more exotic stuff...

    However, you have forgotten WHY the 'rare-earths' are so rare... They are rare largely because they form
    dense compounds that SINK inside large bodies like the Earth [Which is why asteroid mining is potentially
    so lucrative] and are thus not available on the surface, which is dominated by light compounds.

    As building a Dyson sphere/swarm requires disassembling planets for materiel, this is not a problem.

    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.


    Yes, a Dyson sphere should give out huge amounts of IR....

    How about a partially built just started Dyson Sphere...

    Highly reflective mirrors could be quite cool, [certainly cooler than the star they are occluding] and the hot
    objects should be the solar collectors.

    If they are behind the mirrors/radiating preferentially in a different direction, they might not have been spotted.

    As I/the scientists involved have said this is a very low probability scenario.

    But you keep poo-pooing the idea as being totally non-viable with objections that are trivial to counter.

    That's bias, not skepticism.
  14. Standard member sonhouse
    Fast and Curious
    17 Oct '15 18:10
    Originally posted by googlefudge
    [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.
    The 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.
  15. 17 Oct '15 20:43
    Originally posted by DeepThought
    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.
    I did not know that. Interesting. Does it apply to a ring too?

    ..... displacement that could be very hard to control ...
    But it could be done by letting varying amounts of energy through the sphere ....

    lso you need to have enough solar cells to make this possible and they use rare earths.
    I doubt that all solar cells require rare earths.

    building the sphere is a bit of a waste of effort if you can't cover the entire interior with solar energy collectors.
    Assuming you are collecting light. It would work just as well if the idea was to collect heat, in which case solar cells might not even be required. Simply having water cycling from the hot side to the cool side with turbines in between would work quite well, as would many other heat transfer engine designs.

    But the real giveaway ...
    I think the real giveaway is that there is no good reason to think a dyson sphere would emit variable amounts of radiation unless it was being used for signalling. So unless we see a message in the variability there is no good reason to think a dyson sphere or any other alien activity is involved.