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Comets Can't Explain Weird 'Alien Megastructure' Star After All (newscientist.com)
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."
I'm not saying it's aliens but it's aliens!
Tonight on the History Channel.
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.
... 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."
This happened over 1,400 years ago!!
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.