Slashdot Mirror

← Back to Stories (view on slashdot.org)

Comets Can't Explain Weird 'Alien Megastructure' Star After All (newscientist.com)

Posted by samzenpus on from the real-head-scratcher dept.

schwit1 sends the latest news about KIC 8462852, the star that that led many to learn what a Dyson Sphere is. New Scientist reports: "The weirdest star in the cosmos just got a lot weirder. And yes, it might be aliens. Known as KIC 8462852, or Tabby's star, it has been baffling astronomers for the past few months after a team of researchers noticed its light seemed to be dipping in brightness in bizarre ways. Proposed explanations ranged from a cloud of comets to orbiting 'alien megastructures'. Now an analysis of historical observations reveals the star has been gradually dimming for over a century, leaving everyone scratching their heads as to the cause. Bradley Schaefer of Louisiana State University saw the same century-long dimming in his manual readings, and calculated that it would require 648,000 comets, each 200 kilometres wide, to have passed by the star — completely implausible, he says. 'The comet-family idea was reasonably put forth as the best of the proposals, even while acknowledging that they all were a poor lot,' he says. 'But now we have a refutation of the idea, and indeed, of all published ideas.' 'This presents some trouble for the comet hypothesis,' says Boyajian. 'We need more data through continuous monitoring to figure out what is going on.' What about those alien megastructures? Schafer is unconvinced. 'The alien-megastructure idea runs wrong with my new observations,' he says, as he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century. What's more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby's star appears normal, he says."

42 of 412 comments (clear)

  1. Now... by Anonymous Coward · · Score: 5, Funny

    I'm not saying it's aliens but it's aliens!

    1. Re:Now... by Anonymous Coward · · Score: 5, Interesting

      Schaefer makes two VERY large assumptions in discounting the alien megastructure theory. The first being that the energy storage inefficiency would be large enough to create large amounts of infrared light, and the second being that the megastructures in question would have been initially constructed around the star, instead of being moved into place afterwards.

    2. Re: Now... by guruevi · · Score: 4, Insightful

      That and that if you're capable of doing this you can't do 20% of a star in 100y time. Look at the advances we've made in computer and building technology, even space tech in the last century and we as a species are just starting. Give us a thousand years at the current rate of progress and if we haven't killed ourselves we can probably strip mine a planet like Mars to build our energy structures.

      --
      Custom electronics and digital signage for your business: www.evcircuits.com
    3. Re: Now... by tysonedwards · · Score: 4, Informative

      Our star loses one billion kilograms per second... While that may sound like a lot... It's still only an earth mass every 150 million years. The math doesn't work out. Additional matter would need to come from somewhere.

      --
      Thirty four characters live here.
    4. Re: Now... by ShanghaiBill · · Score: 4, Informative

      but you would need to mine 100 planets like mars in the time, kind of.

      Nope. Just one is enough. To build a Dyson sphere at one AU (the distance of the earth from the sun), or about 150,000,000 km, the sphere would have an area of 4 * pi * r^2 = 9e23 m^2. The mass of Mars is 6.39 × 10^23 kg. So if you build the sphere with a mass of about 1 kg / meter squared, you could do it with just a little over one Mars sized planet.

    5. Re:Now... by wierd_w · · Score: 4, Interesting

      There's another possibility that's just as far out, and would explain the missing IR.

      It's a traffic hub for small FTL ships.

      If they use something like an alcubierre metric based warp drive, then the gravitational fields around the craft will scatter the star's light into vectors that are no longer straight lines away from the star. This will result in the star's effective brightness being reduced.

      Get enough of them going in and out of the system routinely, and you will get the observed phenomenon.

      To me, the obvious thing to do is look for gravitational waves coming from the system. If you can't catch their broadcasts (because they use something other than open channel radio), then look for the propwash.

    6. Re: Now... by Anonymous Coward · · Score: 2, Insightful

      A "cloud" is not really excluded.
      A cloud near the dimming star is excluded, because it'd mean more IR (just like a Dyson sphere would).

      However, a cloud might be drifting in midway between earth and this star. The result of that could very well be 20% dimming over 100 years - and no extra IR. No IR because the in-between cloud is too far away from the star to be heated up.

      As for the faster irregular variations, it might be 2 or more darker companions stars close to one bright star. The three-body problem is unsolved, and simulations show irregular unpredictable orbits when 3 (or more) stars orbit all with about the same distance from a common center. You could get irregular blinking as the bright star sometimes pass behind one darker companion, and sometimes behind two others.

    7. Re: Now... by maeka · · Score: 2

      If you had direct energy to matter conversion you'd have the easier matter to energy conversion down pat and converting Mars to energy would be a more efficient use than using it to build a Dyson sphere.

    8. Re: Now... by Anonymous Coward · · Score: 2, Interesting

      Fair enough, but building the Dyson sphere may generate more pork for your home state.

    9. Re:Now... by dreamchaser · · Score: 4, Insightful

      I know you're joking, but sending nukes to attack a civilization with engineering advanced enough to build a Dyson Sphere or other mega-structures would probably be like ants developing the technology to throw grains of sand at relatively low velocities at us.

    10. Re: Now... by pscottdv · · Score: 2

      You should make contact with the astronomers that wrote the paper and tell them your great ideas. I'm sure they haven't thought of them.

      --

      this signature has been removed due to a DMCA takedown notice

    11. Re: Now... by wierd_w · · Score: 2, Interesting

      Oh my, I have been insulted by an anonymous coward. Whatever shall I do? /s

      go invent conspiracy theories about "space nutters" somewhere else, dumbass. The argument that there are no aliens out there loses steam daily as missions like Kepler give statistical samplings of planetary system compositions. The suggestion of it being from FTL use is less convoluted than the suggestion that it is a Dyson swarm, because FTL is going to be an essential technology to construct a dyson swarm. I threw it out there, not because I believed it was true, but because it was a similarly improbable reasoning for the observed phenomenon, and suggested a means to disprove it.

      That's significantly better than jumping whole horse on the ad hominem fun ride, like you just did.

      Catch you later AC.

    12. Re: Now... by arth1 · · Score: 2

      Ah, I see you're grasping at some way to refute my argument with word play. "We", of course, is the human species. A thousand years is not enough for evolution to make much of a dent, "we" means if we could travel in time we'd fit right in. Now a million years ago there was no human race, and in another million there won't be one either. Evolution is still happening.

      Is it, though? Haven't we largely thwarted evolution, and replaced it with survival of everyone we like? We do our utmost to remove any evolutionary pressure, and save people who would have died if it weren't for our own direct intervention. We spend resources on fertility treatments. We do as much as we can to level the playing field and avoid evolutionary competition.

      A thousand years of devolution is more than enough to make a rather large difference.

    13. Re:Now... by silentcoder · · Score: 5, Interesting

      Considering that even if we could launch nukes at light-speed (Which we can't - nothing remotely close) they wouldn't get there for a millenium and a half - it's already too late.

      Whatever it is we're witnessing now, actually happened around 600AD - when we were busy trying to invent a better horse-collar.

      --
      Unicode killed the ASCII-art *
    14. Re: Now... by vivian · · Score: 2

      My current favourite crack-pot theory is Its a star encompassing solar farm being built to power a galactic wide AI. About 90% of start have been covered now - we call all those ones 'dark matter'

    15. Re:Now... by Immerman · · Score: 2

      Except a nuke would probably still be pretty destructive unless they had defensive systems in place. So more like if ants started throwing firecrackers. Not a serious threat under most circumstances, but annoying enough that you might decide to eliminate the problem by some means.

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
    16. Re:Now... by ewibble · · Score: 4, Insightful

      A nuke would not be very destructive at all, our sun is 1,300,000 times larger than the earth (so about 11911 times the surface area) a dyson sphere is larger than the star. When they say we have enough nukes to destroy the earth many times over they don't mean blow it into tiny pieces just destroy all life on earth.

      Also a structure that size would have to withstand large astronomical objects hitting it from time to time.
      if a large 16km asteroid it the earth it would be equivalent to a 200 Million megaton impact(http://www.astronomycafe.net/qadir/q975.html) the biggest nuke ever made is only 50 megatons, that is 4 million times more. Even a 75 meter asteroid has a 100 Megaton impact. Basically if we could send a nuke that far into space the kinetic energy would probably be more than the explosion. And an object that size would be already dealing with things much bigger than a nuke on a regular basis.

      also from here http://www.space.com/51-astero... asteroids can reach up to 940 km across, not 16km.

  2. Alien Megastructures: by ZecretZquirrel · · Score: 5, Funny

    Tonight on the History Channel.

    1. Re:Alien Megastructures: by Applehu+Akbar · · Score: 4, Funny

      "Tonight on the History Channel."

      But where does Hitler come into it?

    2. Re:Alien Megastructures: by lord_mike · · Score: 4, Funny

      It's a secret weapon of the Luftwaffe... tonight at 8pm.

    3. Re:Alien Megastructures: by PolygamousRanchKid+ · · Score: 5, Funny

      Accually, the Luftwaffe did build an airbase on the Moon: https://en.wikipedia.org/wiki/...

      However, the whole project got derailed, when the astronauts discovered the nudist colony on the Moon: https://en.wikipedia.org/wiki/...

      They had the choice of fighting for the master race, or playing naked volleyball with chicks who had 60's style Russ Meyer breasts.

      They "did the right thing . . . "

      --
      Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
  3. It's Primes by justin12345 · · Score: 2, Insightful

    Send quantuum busters, we won't get a Second Chance.

    --
    Cool art gallery, if you're into that sort of thing.
  4. Maybe they're not building it... by Etherwalk · · Score: 2

    even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century. --Summary

    So maybe the aliens aren't building it. Maybe they're just moving it... towards us...

    1. Re:Maybe they're not building it... by cdsparrow · · Score: 2

      I love it when people make judgements on the capabilities of an alien race. By definition, they are alien, so we can make no generalizations. But ostensibly since we can't conceive of a method of building a dyson sphere in 100 years, that means nobody else can either... Personally I bet someone screwed up and dropped a heavy element into the star with an errant stargate and now the star is going through death convulsions.

  5. "just a century"? by jeffb+(2.718) · · Score: 5, Interesting

    If you're willing to believe in a civilization capable of building a Dyson sphere, how much more of a stretch is it to believe they could do it in a few centuries? (We've just been seeing a dimming signal over that period, not complete extinction of the star's light.)

    I mean, yeah, I have some idea of the energies involved, and I'm not sure I can envision a process that would run at that pace producing anything other than streams of plasma at gamma-ray temperatures. But then again, I'm not sure I can envision a process that would digest entire planets worth of material and cast it into a shell at any pace. Good thing I didn't accept that particular process-design gig, I guess.

    1. Re: "just a century"? by bill_mcgonigle · · Score: 5, Insightful

      The surprise would be if a Class-whatever civilization that's building a Dyson Sphere hadn't already mastered self-assembling, self-replicating construction processes. There should be an exponential increase in the rate over time, if we haven't already missed that window. As the buildbots consume the planets, you just get more buildbots until the number is sufficient. Or if the sphere is to be made of the bots themselves then there's no need for a tail-off. Clarke called 'em monoliths when he had them eat Jupiter, but same idea.

      --
      My God, it's Full of Source!
      OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
    2. Re:"just a century"? by Chrontius · · Score: 3, Interesting

      If they seeded our planet with life using FTL drives, the light of their civilization's dawn could just be reaching us now. If we accept the given of rare garden worlds, and cosmic gardening, the odds of seeing this are actually quite good.

    3. Re: "just a century"? by zmooc · · Score: 2

      Buildbots probably wouldn't consume planets; escaping from their gravity well would be much too costly compared to the alternatives. They probably would use asteroids instead, taking their time to tweak their orbits so they arrive at their destination processing plant with a minimum amount of energy. This would almost certainly not happen at an exponential rate. As with all mining, they would start with the low hanging fruit, causing production to become increasingly more difficult as time passes, prohibiting durable exponential growth.

      Also, while I'm typing a comment anyway, the Dyson sphere would probably reflect raditation to several power stations within it. These might very well redistribute it by simply reflecting it back out, for example to stations in the outer star system, from where it can be redistributed to their mining sites (perhaps even simply blasting asteroids with radiation in order to control their orbits). This would cause the radiation from the Dyson sphere that Schafer expects to come from somewhere else entirely and probably not in a uniform way at all; we might very well not even be able to detect it or would perhaps discount short bursts of radiation reflected from asteroids as being noise. I can imagine their entire star system to look like a giant beautiful collection of laser scanners ;)

      --
      0x or or snor perron?!
  6. Inconceivable! by Anonymous Coward · · Score: 5, Insightful

    ... he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century.

    Clarke's first law: "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."

  7. Re:From the wisdom of Sherlock Holmes... by Jeremi · · Score: 4, Funny

    "Sherlock Holmes observed that once you have eliminated the impossible then whatever remains, however improbable, must be the answer. I, however, do not like to eliminate the impossible."
    - Douglas Adams, Dirk Gently's Holistic Detective Agency

    --


    I don't care if it's 90,000 hectares. That lake was not my doing.
  8. What about the "hot pole" theory? by Anonymous Coward · · Score: 4, Insightful

    This star is larger than our Sun, yet it rotates thirty times faster. Its poles are significantly flatter, hotter, and brighter than the rest of the star. Thus a large object could block 22% of the star's light while covering a much smaller percentage of its disk. This also explains why the dips in the light curve are pointed on the bottom, not flat.

    There could also be a large unseen planet (i.e. one that does not transit the star from our point of view) pulling on the star's tidal bulge and causing its visible pole to slowly precess away from us. That would explain the gradual dimming.

    1. Re:What about the "hot pole" theory? by wonkey_monkey · · Score: 2

      ... hot pole ... bottom ... bulge ...

      That is all.

      --
      systemd is Roko's Basilisk.
    2. Re:What about the "hot pole" theory? by D'Eyncourt · · Score: 5, Interesting

      There are a couple of problems with your ideas.

      Basically the most any planet in any star system could cover is approximately 2% of a star during a transit (as a comparison a transiting Jupiter seen from another star system would cover about 1% of the Sun). This is despite our estimate of when a planetary body would become massive enough to become a brown dwarf is about 80 times the mass of Jupiter because the mostly hydrogen gas in any gas giant is highly compressible. A planet with twice the mass as Jupiter would have a diameter only slightly larger than that of Jupiter, very much less than the 1.26 (= 2^[1/3]) growth that would be expected by simple linear growth.

      If a body instead were large enough to become a brown dwarf, then the interplay of the light being generated by fusion at its core becomes more important and its size would balloon out to many times that of Jupiter. And, of course, a brown dwarf would be easily detectable spectroscopically.

      Thus ANY planet in orbit around Tabby's Star that was transiting in front of it simply could not cause the brightness of the star to dip by as much as 22% as was once seen. There is the FAINT possibility that somehow what was observed was a planet within our own Kuiper Belt that happened to transit Tabby's Star during Kepler's observations, and that being MUCH closer to Earth than Tabby's Star's distance of about 1500 light years would allow it to cover more of that star, but there is the problem that a Kuiper Belt gas-/ice-giant should have been glaring obvious to our Spitzer Space Telescope which specializes in the infra-red range.

      Your idea of the dimmer poles precessing towards us contains contradictory ideas: the planet causing this somehow has to be massive AND close enough to cause this, and yet has to have an orbit that is at least a couple of hundred Earth-years in length. This "newly" detected dimming was determined from photographic plates taken at different times from 1890 to around 1990.

      My suspicion is that what we may be watching is a relatively short-lived (meaning less than tens of thousands of years) phase of Tabby's Star evolving from a main sequence star at the very earliest stage of becoming a (super-)giant. There is just barely enough helium accumulated at its core that its fusion only fitfully begins only to sputter out when the additional heat generated by that hotter fusion diffuses that core to below helium-fusion levels. Of course this "current" sputtering was generated tens to hundreds of thousands of years ago at the core (taking that long for the scattered light to reach the star's photosphere and thus become visible to us), but when helium fusion actually takes hold then the star ballooning out to become a (super-)giant will overtake that sputtering.

    3. Re:What about the "hot pole" theory? by drinkypoo · · Score: 2

      People who post genuinely insightful comments as ACs do the rest of us a great disservice by not logging in, since we have to wade through the shitcakes to find the quality comments. You can have a slashdot login and remain anonymous, since Slashdot does not have a real name requirement.

      If you have something meaningful to say, please log in. To do otherwise is to provide cover to trolls.

      --
      "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
  9. Planetary breakup? by Anonymous Coward · · Score: 2, Insightful

    Roche limit reached about a century and a half ago, breakup continues. A super sized rocky planet which has migrated to within Mercury like distance of it's star and has subsequently been pulled apart. Put the planet in an orbit which is nearly edge on (which it would have to be to be detectable using these methods) and as the debris cloud increases in size the star is progressively dimmed (from our point of view) more and more.

    Seems the most obvious explanation.

    Interestingly, if you did want make a dyson sphere and you wanted a way to break up some planets to get access to the raw materials then causing them to shift orbits closer to the star might be a way to do it.

    Planetary collision, leading to two planets breaking up? There really are all sorts of possible explanations without going straight to dyson sphere builders.

  10. Re:ok.. Come on... by Anonymous Coward · · Score: 3, Informative

    > So right here, on planet Earth, the same types of people - scientists - are incapable of understanding how a large structure the size of the pyramids was built a couple thousand years ago..

    There are lots of theories; there's no particular surprise that they were able to, but we don't know exactly how it was done because it was a long time ago and the Egyptian engineers didn't leave very good records. Nobody is going to be able to prove within a shadow of a doubt how it was done, but there are lots of plausible ways it could have been done.

    https://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques#Construction_method_hypotheses

  11. This is old news by Smiddi · · Score: 5, Funny

    This happened over 1,400 years ago!!

  12. perhaps we should consider the obvious. by Gravis+Zero · · Score: 4, Funny

    maybe the star isn't screwed in tightly enough. just give it a half twist and see if that stops the flickering. ;)

    --
    Anons need not reply. Questions end with a question mark.
  13. Re:"Old" news by stealth_finger · · Score: 3

    I beg your pardon, but this is already old news. It has been relayed by other channels at least two days ago. If /. still want to pretend being news for nerds, they have to catch up and post news when they are news, not two days later.

    This comment is old news. Seeing as slashdot isn't a news site it's always been like that, it has no writers or reporters. All it is, is some people that put up interesting articles from elsewhere and then we all bitch and moan about all kinds of things, sometimes the original article may get a mention or may not depending how it goes.

    --
    Wanna buy a shirt?
    https://www.redbubble.com/people/stealthfinger/shop?asc=u
  14. Re:flush by CrimsonAvenger · · Score: 2

    "A Logic Named Joe" by Murray Leinster (1946).

    Mr. Leinster, at least, seems to have imagined some of the technology that our children use today. And he was a decade older than MY grandparents (and I'll be a grandfather soon).

    But your point is still reasonable, if a longer timeline is used. Why should we expect that Charlemagne should have anticipated the modern world? And we should we think that we can anticipate the limits of the possible for our descendants in 1200 years (for those of you who are unaware of "Big Charlie", he was crowned Holy Roman Emperor in 800AD (and yes, it was neither Holy, nor Roman, nor an Empire, but that's what history likes to call it anyway - deal))?

    --

    "I do not agree with what you say, but I will defend to the death your right to say it"
  15. Re:What if it's not local to the star? by abies · · Score: 2

    Not sure about exact proportions, but Earth is rotating around the Sun. I have a feeling that anything in Oort cloud, big enough to dim that star regardless of position of Earth around a Sun, would also dim certain others stars nearby (in angle terms).

  16. Dyson Sphere can not exist! by jraff2 · · Score: 2

    Attempting to build a entirely enclosed sphere around a star would result in MASSIVE support structure to hold the top and bottom away from the star, almost impossible! Yeah one could have a ring or partial sphere, but not the whole thing. It would collapse.