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KIC 8462852: Fading in the Kepler Data

Those of you who have been following the controversy over the dimming of KIC 8462852 (Tabby’s Star) may remember an interesting note at the end of Bradley Schaefer’s last post on Centauri Dreams. Schaefer (Louisiana State University) had gone through his reasoning for finding a long-term dimming of the star in the DASCH (Digital Access to a Sky Century@Harvard) database. His third point about the star had to do with the work of Ben Montet (Caltech) and Joshua Simon (Carnegie Observatories).

Montet and Simon’s work relied on an interesting premise. Tabby’s Star had been discovered because it was in the Kepler field, and thus we had high-quality data on its behavior, the unusual light curves that the Planet Hunters team brought to the attention of Tabetha Boyajian. As the researchers note in a new paper, Kepler found ten significant dips in the light curve over the timespan of the Kepler mission, dips that were not only aperiodic but irregular in shape, and that varied enormously, from fractions of one percent up to 20% of the total flux of KIC 8462852.


Image: Montage of flux time series for KIC 8462852 showing different portions of the 4-year Kepler observations with different vertical scalings. Panel ‘(c)’ is a blowup of the dip near day 793, (D800). The remaining three panels, ‘(d)’, ‘(e)’, and ‘(f)’, explore the dips which occur during the 90-day interval from day 1490 to day 1580 (D1500). Credit: Boyajian et al., 2015.

Schaefer noted in his Centauri Dreams post (see Further Thoughts on the Dimming of KIC 8462852) that if Tabby’s Star were actually fading at a rate of 0.164 mag/cen, then it should have undergone fading during the period it was under observation by Kepler (in fact, it should have faded by 0.0073 mag over the Kepler lifetime on the main Cygnus field). Montet and Simon have now presented us with their analysis in a paper just up on the arXiv server.

A fading of the kind Schaefer described would be well above the photometric precision of the Kepler instrument. Montet and Simon realized they could search for long-term trends by using the full-frame images (FFI) collected during the Kepler mission. Eight of these were recorded at the beginning of the mission, with another FFI recorded each month throughout the mission. Given that the mission lasted four years, a star dimming at the rate Schaefer suggests should decrease in brightness by 0.6% over the Kepler baseline. And as the authors point out, using FFI data avoids the removal of the dimming trend by the data processing pipeline.

The results: The study, which worked with KIC 8462852 and seven nearby comparison stars, found that in the first three years of the Kepler mission, Tabby’s Star dimmed at a rate of 0.341%±0.041% per year. Over the next six months, it decreased in brightness by 2.5%, and then stayed at that level during the duration of the primary Kepler mission. The paper continues:

We then compare this result to a similar analysis of other stars of similar brightness on the same detector, as well as stars with similar stellar properties, as listed in the KIC, in the Kepler field. We find that 0.5% of stars on the same detector and 0.7% of stars with similar stellar properties exhibit a long-term trend consistent with that observed for KIC 8462852 during the first three years of the Kepler mission. However, in no cases do we observe a flux decrement as extreme as the 2.5% dip observed in Quarters 12-14 of the mission. The total brightness change of KIC 8462852 is also larger than that of any other star we have identified in the Kepler images.

Screenshot from 2016-08-05 11:11:46

Image: Photometry of KIC 8462852 as measured from the FFI data. The four colors and shapes (green squares, black circles, red diamonds, and blue triangles) represent measurements from the four separate channels the starlight reaches as the telescope rolls. The four subpanels show flux from each particular detector individually. The main figure combines all observations together; we apply three linear offsets to the data from different channels to minimize the scatter to a linear fit to the first 1100 days of data. In all four channels, the photometry is consistent with a linear decrease in flux for the first three years of the mission, followed by a rapid decrease in flux of ≈ 2.5% over the next six months. The light gray curve represents one possible Kepler long cadence light curve consistent with the FFI photometry created by fitting a spline to the FFI photometry as described in Section 4. The large dips observed by Boyajian et al. (2016) are visible but narrow relative to the cadence of FFI observations. The long cadence data behind this figure are available online. Credit: Montet & Simon.

M. A. Thompson (University of Hertfordshire) and colleagues published a recent study in Monthly Notices of the Royal Astronomical Society reporting their findings using millimetre and sub-millimetre photometry. The paper finds that a dust cloud orbiting Tabby’s Star would have to be no larger than 7.7 Earth masses of material within a radius of 200 AU, adding “Such low limits for the inner system make the catastrophic planetary disruption hypothesis unlikely.”

Montet and Simon don’t necessarily agree, but in any case there are other problems. The authors think the light curve is “…consistent with the transit of a cloud of optically thick material orbiting the star,” and that such a cloud could be small enough to meet Thompson and team’s requirements. The breakup of a small body or a recent collision producing a large dust cloud could also produce a cometary family that transited the host star as a single group. But we’re still not out of the woods:

To explain the transit ingress timescale, the cloud would need to be at impossibly large distances from the star or be slowly increasing in surface density. The flat bottom of the transit would then suggest a rapid transition into a region of uniform density in the cloud, which then continues to transit the star for at least the next year of the Kepler mission. Moreover, such a model does not naturally account for the long-term dimming in the light curve observed in both DASCH and the Kepler FFI data, suggesting that this idea is, at best, incomplete.

A deeply mysterious star, our KIC 846285. Montet and Simon call for alternative hypotheses and new data to help us explain existing observations, and we can be glad to have Tabetha Boyajian’s team on the case thanks to the success of the recent Kickstarter campaign. Observations are already in progress at the Las Cumbres Observatory Global Telescope Network, and the Kickstarter funds will take us deep into 2017. For more on the Las Cumbres work, see Corey Powell’s recent interview with Boyajian for Discover Magazine, from which this:

From our new observations, we’ll be able to tell a lot about the material that’s passing in front of the star: if it’s some kind of dusty thing, some kind of solid thing. [Boyajian’s working hypothesis is that the dimming is caused by a huge swarm of comets, set loose perhaps by some cataclysmic event around the star.] What’s also important is that we will also get a baseline of spectral observations so we can look at if there’s any radial velocity shift or if there’s any variable emission of the lines, things we’d expect comets to have.

The paper is Montet and Simon, “KIC 8462852 Faded Throughout the Kepler Mission,” submitted to the AAS Journals and available as a preprint. The Thompson paper on circumstellar dust in this system is “Constraints on the circumstellar dust around KIC 8462852,” published online by Monthly Notices of the Royal Astronomical Society 25 February 2016.


Comments on this entry are closed.

  • ljk August 5, 2016, 12:18

    How Astronomers Plan to Solve the Mystery of the “Alien Megastructure Star”

    By Corey S. Powell

    July 31, 2016 11:10 pm

    If you look in enough places, eventually you’ll find something profoundly strange. That’s been a reliable rule of thumb through the history of science, and last year it proved dramatically true again for astronomer Tabetha Boyajian. While digging through data from NASA’s Kepler space telescope, which has been monitoring 150,000 stars for signs of orbiting planets, she realized that one of these things is not like the others. A single star in that set, formally catalogued as KIC 8462852 but informally known as Tabby’s Star, flickers in an inexplicable way: unlike the shadows produced by planets, unlike any known type of stellar pulsation, simply unlike anything seen before.

    Tabby’s Star is so unusual that a few scientists, including Boyajian’s colleague Jason Wright, raised the possibility that its flickering is not natural but is due to the presence of an enormous artificial construct. That speculation quickly lent KIC 8462852 another nickname, the “alien megastructure star,” and prompted a flood of breathless news stories; it even got a shout out on Saturday Night Live. Boyajian’s subsequent TED lecture drew even more attention to her star.

    Now Boyajian, who recently joined the faculty of Louisiana State University, faces the daunting task of sorting through a wide range of potential explanations, from mundane to bizarre. You will probably not be surprised to hear that she’s not a big fan of the space-alien theory, but even the more sober scientific ideas are plenty exotic. I spoke with Boyajian about how she intends to solve her mystery—and about the surprising ways that institutional science is stacked against exploratory research that is not guaranteed to lead to clear answers.

    Full interview here:


    To quote:

    The tone of the news reports were not conflicted at all, of course; they were downright giddy, playing up the possibility that we were seeing an alien artifact around a distant star. How did you feel about that response?

    I would definitely say it’s been overwhelming. Even in the very good articles that have been written about the star, the title is often leading. Some people don’t do responsible reporting and take it one step further. You know, it is what it is. I didn’t expect this level of excitement at all, but in retrospect I should have!


    It seems like there should be a way to carry out this kind of purely exploratory research without having to resort to Kickstarter or the like. What do you think?

    Just to be clear, we have the support of tons of astronomers. Kickstarter doesn’t have to be peer reviewed, but nobody has said, this is bullshit, you can’t do that, you should be doing science. Everybody understands our point of view. The peer review process works really well overall, but it [isn’t appropriate when] the probability of having results at the end of the year is very low. Having a different, government-funded channel for scientists to do higher-risk proposals would definitely allow a lot of other cool science to get done.

  • Harry R Ray August 5, 2016, 13:00

    A question for Montet and Simon: Is there any way you can tease a possible REDDENING of KIC8462852 out of JUST the Kepler data for the four year period. The reason I mention this is: ASSUMING NO long term brightness variation of the nearby(companion or not)M(dwarf or not)star, a dimming of the primary star ONLY would mean MORE red in the TOTAL SPECTRUM! ALSO: The first thing you should do on September 24 should be to access the Gaia data on KIC8462852(and the companion star if Gaia is sensitive enough to resolve it from the primary star).

    • Michael T August 5, 2016, 20:53

      Interesting question, but doesn’t reddening also depend on the absorbtion spectrum of the occulting material?


  • tchernik August 5, 2016, 13:22

    Seems like a lot more study of it is warranted, given the confirmation of dimming in this star’s luminosity. At least something very unusual but natural is happening there.

    Maybe something not so natural.

    And yes, this star continues to be the most mysterious one in the galaxy.

  • Paul Carr August 5, 2016, 14:37

    I am interviewing Ben Montet’s for the Wow! Signal in Monday. Any questions NOT clearly answered in the paper?

    • EricSECT August 5, 2016, 20:43

      Yes, I have a question Paul and please let us know ASAP when we can read or listen to that podcast!

      The paper states “…We find that 0.5% of stars on the same detector and 0.7% of stars with similar stellar properties exhibit a long-term trend consistent with that observed for KIC 8462852 during the first three years of the Kepler mission…. ” Is there some kind of an theory or explanation for that? Instrumentation? Astrophysical? Were these anomalous stars near Tabby’s?

      My new prediction for the future of Tabby’s Star. We will never observe any further major dimming events!

    • EricSECT August 6, 2016, 5:46

      Paul Carr;
      Could you please ask about the other stars -the 0.5% (“same detector”) and the 0.7% (“similar stellar properties”)-that exhibit the 3 year long term trend dimming? I would like to scrutinize their light curves and need to know their designators in the Kepler database (KIC xxxxxx, etc). Thanks!

  • Wojciech J August 5, 2016, 15:10

    And yet it dims!

    • Sean Meaney August 10, 2016, 3:01

      I put it down to a hydrogen flowthrough in our direction. Star and Planets in system function as gravity scoops creating gaps in the hydrogen of a varying nature over time. I assume stars go boom and spill hydrogen in our direction.

  • Ashley Baldwin August 5, 2016, 19:06

    Great review. Thanks as ever- what an incredibly thought provoking subject matter and a great advert for observational science . It always turns up surprises. Just wait till TESS,WFIRST ,PLATO and JWST report back !

    Trying to look for more prosaic explanations of this impressive stellar dimming made me reflect on intrinsic , stellar causes which have been a bit ( perhaps understandably so given the atypical phenomenum) a bit sidelined by cometary / Interstellar dust clouds and megastructures and such the like.

    The star itself is now being described as being partially “evolved” , in other words has begun to run out of hydrogen to fuse in its core and is moving off the erstwhile main sequence ( that period of a star’s life from birth that it produces energy by fusing hydrogen in its core ) . This in an interesting time for all stars with their future progress ironically determined by starting main sequence mass. With F dwarf stars especially .

    KIC 8462852 is a larger F dwarf , spectral type F3 , with a starting mass of about 40 % more than the Sun. Not a huge amount but given the exquisite sensitivity of fusion reaction rate ( and type ) to mass this has big implications to both the type of hydrogen fusion but also , critically the star’s internal architecture . Stick with me!

    Ultimately stars fuse six hydrogen nuclei ( protons ) to produce 3 helium nuclei with the small reduction in mass between beginning and end of about 0.7 % going to produce energy in the form of gamma rays and neutrinos (which don’t much interact with mass and can for simplicity sake be ignored here) . Although 0.7% doesn’t sound a lot when one adds up the vast supply of hydrogen available for use , this produces a lot of energy . More than enough to resists the inward pull of gravity that created the intense heat and pressures required to start the whole process off and to produce a counterbalancing outer radiation force that maintains the star in a state of “dynamic equilibrium” for as long as it is on on the main sequence . Over simplified but there are two ways to use the six hydrogen nucleii to get your energy and helium . Firstly the so called “proton/ proton track mentioned above and used preminsntky in stars of less than about 10-20 % greater mass than the Sun ( like Alpha Centauri) or the so called “CNO” process that in essence uses Carbon , Hydrogen and Oxygen as catalysts enroute to producing the helium and energy . This latter process is much more efficient than the “pp” process , releasing far more energy and is the main reason why stars with larger mass counterintuitively tend to have shorter lives . It needs the higher temperatures and pressures created through mass related gravitational contraction , hence the inverse mass / lifetime arrangement . Hydrogen fusion starts reliably at about 15 million K via pp, with higher temperatures starting in the nucleii of marginal bigger than the Sun stars driving the CNO process.

    So where does all this connect with Tabby’s star ? Internal stellar architecture. In addition to greater heat and fusion , larger mass stars have convective cores . The same process of fluid movement seen in a boiling pan by which less dense liquid rises before cooling and the falling to create a cyclic process. Stars up to the mass of the Sun release their core heat though radiation ( how we feel the heat of the stove that’s heating that converting pan ) , until convection finally takes over about two thirds of the way to the surface. This means that heat transfer takes longer in smaller stars ( hundreds of thousands of years ) but crucially ,core convection starts with F class stars , particularly bigger types such as F3 Tabby’s star . It allows rapid transfer of the energy of fusion as well as allowing hot plasma to mix with hydrogen surrounding the star’s core thus allowing it to fuse too in a way impossible in sun size and smaller stars .. ( helping partially compensate for the foreshortening effect of greater mass) . As stated this effect first becomes very marked in larger F class stars with great globules of supper heated plasma mixing with peri nuclear hydrogen , even overcoming the usual heavy fluid resistance to convection known as the Schwartzchild criterium. So called “overshoots” . All of this utilises an F dwarf’s hydrogen more substantially than say the Sun ( which can only fuse in its core and not convect outwards from there , thus only having access to a paltry 10 % of its total hydrogen load- something a Kardashev II civilisation might want to look at if they want to prolongue their G type star’s main sequence life ) remaining on the main sequence longer than they should for their size .

    Consequently F dwarfs atypically only have a short time of a couple of hundred years as a red giant ( compared to the Sun’s 2 billion) and huge and rapid increases in size and related luminosity ( up to a 1000 times ) as they leaves the main sequence . Everything is speeded up. So I can see why an F3 evolved star like KIC8462852 could INCREASE in luminosity over short periods thanks to these fusing convective core overshoots. However, I wondered given the short lived nature of these phenomena if when they finally become cooler and denser and collapse back into the stellar core that there are then “short” periods of relatively reduced size and luminosity . Short here still being hundreds or thousands of years though still only the blinking of an eye on stellar evolution timescales .

    I note that the study does find similar ( but much less pronounced .) dimming in type matched stars which may support this . We are after all only getting a very brief snap shot of the star ( even with the old photographic plates ) and its peers , so even extending observation won’t necessarily do anything more than show ongoing dimming. It’s unlikely to catch the exact moment of an F dwarf suddenly brightening again. If the overshoot concept holds true then there should be early evolved F dwarfs with increased luminosity and a similar arc texture or “asteroseismological” profile .

    Whatever the case , F dwarfs evolution is unique amongst main sequence stars (especially larger types) and especially their early evolution pathway and Tabby’s star with ever more sophisticated asteroseismology might be the ideal star to characterise them in depth .Assuming no coincidence in Tabby’s star being an early evolved star .

    Given the nature of “overshoots” it’s difficult to know as to whether any obvious pattern to variability can be found even if it is intrinsic in nature . That said asteroseismology ( without it there is no exoplanet science ) has grown in parallel with Kepler and with the extended observations to date , and will surely give the better understanding required through investigation of this quirky stellar class and star . A star that doesn’t want to grow up and wants to stay a teenager forever ! Sulks and all.

    • EricSECT August 6, 2016, 6:19

      I think you are on to the correct explanation to this enigmatic star’s behavior.

      Tabby’s Star is about to exit the main sequence and is unstable. Its just pure dumb luck we caught it at this transition. If we scrutinize the Kepler light curves for other stars, we MAY see a handful of stars exhibiting the same behavior, dependent on the duration of this instability. Start with other “F” class stars, there should be about 4500 in the Kepler database, and then expand out to other classes as desired.

      (This is Dirk Bonte’s hypothesis)
      Tabby’s core hydrogen burning is over, out of fuel. The core shrinks and heats up but is not yet hot enough to fuse helium. As the core shrinks it spins faster.

      In the shrinking core, magnetic fields intensify. Stronger magnetic fields that fluctuate randomly in strength, location and duration. We observe this as a variation in light output. The cause of the dimming is by double ionization of helium. Cephid-like mechanism, but this star is NOT a Cephid.

      Supporting evidence/predictions:
      (1) Leading into a major dimming event, would we expect to see helium absorption lines? And then, coming out of the dimming, helium emission lines?
      (2) If the surface of the star shrinks and swells as it cools and heats, it may be possible to detect via radial velocity if sensitive enough.

      • Harry R Ray August 8, 2016, 9:23

        Dirk Bontes has come up with a theory that INCORPOPRATES all of your above points, in EXQUISITE DETAIL! Check it out in the past comments on this star on this website.

      • JonG August 16, 2016, 19:03

        An increase in magnetic field should cause a pronounced Zeeman effect in the emitted light spectrum. Has any such splitting of the spectral lines been seen for this star?

        • EricSECT August 16, 2016, 19:59

          An excellent point. I have no idea but predictions like yours need to be pursued. Is there any place on-line someone like us can look at Tabby’s spectrum? This effect might not manifest itself until the next major dimming event, perhaps along with helium emission and absorption lines changing leading into and then exiting the event?

          • Harry R Ray August 23, 2016, 17:39

            You will need to check with Dirk Bontes DIRECTLY to get that information. Correct me if I am wrong, but I don’t thonk ANY MENTION was made of that in his 2,ooo word essay/”book” on the subject. Also check out the https://astronomytopicoftheday.wordpress.com website for the LATEST NON-internal POSSIBLE “natural” solution to the KIC8462852 problem. If Gaia CONFERMS that the distance to KIC8462852 IS 1480 light-years, on September 24, this becomes a VERY VIABLE ALTERNATIVE to Dirk Bontes’ solution. My guess, however, is that this will NOT LIKELY BE THE CASE, and KIC8462852 will be MUCH CLOSER TO US THAN 1480 AU, yhus COMPLETELY NEGATING the argument on the above-mentioned website.

    • FrankH August 8, 2016, 16:39

      I agree that this is probably the best theory to date.
      There is an analog – red supergiants like Betelgeuse that show clear and huge convection cells in their photospheres.
      A red supergiant is going to be orders of magnitude larger than KIC 8462852, but if large convection cells are rolling up to the surface, we would see a magnitude change without an IR excess.
      KIC 8462852 is too far away (and too small) to resolve with Earth based interferometers but the convection should produce small velocity changes in the spectra.

    • EricSECT August 13, 2016, 7:51

      I hope you don’t mind but I copied and pasted some excerpts from your “Overshoot” suggestion and re-posted at a reddit conversation thread. Forgive me, I don’t think I mangled it!


  • Ashley Baldwin August 6, 2016, 10:49

    Thanks. Nice fir some confirmation of my limited theoretical knowledge . Strange things F dwarfs , occupying a unique niche in the main sequence. I had never paid it much attention before until it actually played out in this case . Ironically thanks to the core convective zone we are presumably seeing fusion of part of the self same hydrogen that would ordinarily fuse later on in the evolutionary process as part of hydrogen shell burning surrounding a fusing helium nucleus once contraction a la Stephan Boltzmann has elevated core pressure and temperature have adequately to allow the customary ” helium flash ” and the usual pathway ( speeded up though) .

    It’s always described and illustrated in the literature as being about increased stellar expansion and luminosity but of cause there have to be ” brief” periods of the opposite thanks to the specific F dwarf mass/ core architecture and the Schwartzchild criterion pulling back the energy overshoots temporarily . Veritable energy waves breaking and receding on a nuclear beach if that image does the process justice. May not by a Dyson Sphere but a great example of the exciting rewards that extended periods of observation can bring though . In a real life example of something rare and only touched upon in the literature if it is indeed the cause of what we see at Tabby”s star.

    • EricSECT August 8, 2016, 6:50

      For supportive evidence, what unique observations will strengthen your (lets call it the “Overshoots”?) hypothesis? For example, we grab a spectrum next major dimming event, if Overshoots is the cause….? Does it predict any stronger or weaker (than normal) emission or absorption lines? Seems like it would be a normal spectrum, just less light output overall. But then…. how would we distinguish Overshoots as cause rather than from some solid structure blocking all wave lengths of light, which also predicts the same spectra change ? Etc.

      • Ashley Baldwin August 8, 2016, 13:37

        It’s a well described phenomena in “F” dwarfs evololution off the main sequence and of course usually gives rise to transient increase in stellar size and luminosity thanks to core convection leading to fusion of hydrogen outside the usual centrally fusing core . Though the dimming periods of the cycle is much shorter lived, but still in terms of hundreds of years ( especially of the old photographic plates evidence holds up) I can’t believe that it won’t turn up in large area prolongued stellar observations over large portions of the sky . ( including tose of the past as more plates are scrutinised in detail) . PLATO as an exoplanet mission comes to mind with a six year primary mission and likely longer . The Large Synoptic Survey Telescope will do too ( along with a whole lot of other unexpected phenomena ) . It is designed to photograph the whole sky with great sensitivity over just a few nights , and will do so for its lifetime . PLATO alone is already 50 % longer the original Kepler mission, with LSST orders of magnitude more . And all stored digitally with no vulnerable photographic plates involved despite their proof of using extended observation periods. The other advantage of missions like PLATO and KEPLeR is that they will hugely increase the understanding of stellar asteroseismology too where surface seismic waves help accurately describe otherwise invisible internal activity/architecture in the same way earthquakes do for the Earth. I’m sure that such missions will not only eventually turn up other similar events to KIC8462852 but also help define it in more detail too.

        • RAS August 9, 2016, 13:24

          Wonderful example there of the implied dismissal of other explanations in that it of course couldn’t be aliens because that would somehow be ‘unnatural’ or to way out, though not stated but instead implied through the very failure to even consider other explanations in that it must be the star. As if the possibility of intelligent life arising elsewhere within the galaxy wasn’t actually a predictable and entirely natural possibility of the very existence of the universe itself.

          • EricSECT August 12, 2016, 5:56

            I for one would sure love to see evidence of ETI in my lifetime, and am positive that it exists out there and that it arises naturally under certain constraints. This is belief based and not objective evidence based.

            Is Tabby’s Star this evidence we seek? Extraordinary claims require extraordinary evidence, and you have to agree that ETI as the cause for Tabby’s dimming fits THAT bill. Also, to avoid the “Aliens of the Gaps” snake pit, first all “Natural” explanations must be considered, weighed for predictive strengths and discarded if they fall short. That’s just how science works. The least contrived hypothesis that is left standing, that can best explain the observations and has made successful prediction is probably correct (but never certain).

            The least contrived hypothesis may turn out to be ETI.

            Me? Looking forward to (first) ALL possible “natural cause” hypothesis offered up for consideration …and then one by one shot down in flames, basically.

  • Giuseppe August 6, 2016, 13:54

    Could Tabby’s star be in a situation similar to what probably happened with the Late Heavy Bombardment- Nice model? About 600 My after the Solar System formation, apparently Jupiter and Saturn went into a 2-1 resonance that destabilized all the system and sent a lot of smaller bodies in eccentric-elongated orbits, eventually smashing into each other and leaving massive craters on the moon.
    If some resonance started between giant planets in that system, we could be looking at a similar scenario. Debris clouds could explain the dips in the light curve while the progressive increase in dust would explain the long term dimming

    • Harry R Ray August 8, 2016, 9:30

      This is EXACTLY THE FOUNDATION for Boyajian et al’s “cometary hypothesis”. However, constant LONG-TERM fading throws a big monkey wrench into this hypothesis, as Schaefer so EMPHATICALLY pointed out.

  • Robert G August 6, 2016, 17:02

    Quick question which may be a silly one. Do we have uv/vis spectra of this star with enough detail to detect relative elemental concentrations? In other words, can we exclude the possibility that there may be something out of line with relative nuclear abundances that would give the normal f type nuclear processes a case of indigestion?

  • ljk August 7, 2016, 19:11

    Could It Be: Possible Signs of Extraterrestrial Intelligence?

    By: David Grinspoon | February 29, 2016

    We need to learn how to talk about possible signs of extraterrestrial intelligence.

    In my most recent column, I discussed the lack of evidence for technically advanced extraterrestrials. Curiously enough, in the time between writing that and its publication, some possible evidence materialized.

    Full article here:


    To quote:

    How to Discuss Extraterrestrial Intelligence

    Some scientists and pundits want to condemn that idea as ridiculous and unworthy of mention. But it would have been wrong not to consider this enticing possibility for such a strange observation. The correct posture, at this point, is to regard an artificial explanation as extremely unlikely — but not illogical or impossible.

    Perhaps this provides a test case, because we have to learn how to talk about these things. In the decades ahead we will be observing more and more exoplanets with better and better instrumentation (see S&T’s October issue for more on that topic). We’ll see some novel things, and when we don’t understand them, then biosignatures and even technosignatures are possible explanations, and we should consider them without going overboard with either skepticism or credulity. We have to be cautious — but if we refuse to consider outlandish and wonderful possibilities, we might miss something truly important.

    The alien hypothesis has increased the interest with which scientists are scrutinizing this star. Out of this will come new knowledge, most likely not about aliens. Promising plans include making new visible, infrared, and ultraviolet observations. The next time the light of KIC 8462852 flickers we can inspect the material properties of the obscuring stuff: Is it dust? A swarm of comets? Or something seemingly artificial? Quite possibly it’s something nobody has thought of yet.

    Perhaps someone will have explained the peculiarities of KIC 8462852’s light curve by the time this column appears in print. On the other hand, the mystery might endure for years, allowing numerous predictions to be made and tested. Imagine all the fiction, fantasy, nonsense, religion, and good science that a possible alien civilization might inspire if generations go by without a definitive answer. It would serve as a fluttering beacon reminding us that we have a lot to learn.

  • ljk August 7, 2016, 20:03

    Saturday, August 6, 2016

    Aliens, Perhaps, but Not the Aliens of the Gaps

    With the publication of Montet and Simon’s arresting new preprint showing even more anomalous behavior by Tabby’s Star, a lot of reasonable people are asking whether it’s time to declare this stellar weirdness the work of an ET civilization, or whether it may be soon. While I am emotionally inclined to go this way, and intuitively sense that this maybe the ultimate conclusion reached, I am not a believer. There is a fundamental error we still must avoid.

    Full article here:


    • Rob Henry August 8, 2016, 20:28

      That article makes a great point in that any worthy evidence for Tabby’s star being an artificial structure should be predictive, yet it refuses to make the obvious one.

      If we are observing a Dyson sphere, then the rate of dimming, and the seeming acceleration of that rate imply its construction is nearing completion. Surely that would require KIC 8462852 to be half the distance or less that we currently think. With the Gaia data release on that very star in just five weeks, it seems perplexing that they didn’t make that prediction. Very odd!

      • ljk August 9, 2016, 8:47

        Aliens tend to scare most humans. Especially the kind that can tear apart entire solar systems and reconstruct them to their liking.

      • Harry R Ray August 9, 2016, 9:33

        I did in my “thought experiment” a few months back. However, if it DOES turn out to be only half the distance it is REPORTED to be, that does not necessarily mean that it IS a Dyson(sphere, ring, shell, swarm, or WHATEVER). It could STILL turn out to be some unknown natural process. Now, turning to the “dark side…”. Jason Wright stated that the light curves of KIC8462852 are only “consistant with” an Alien Megastructure, not that they ACTUALLY ARE! However, AFTER the Montet and Simon paper, I wonder if he has CHANGED HIS POSITION and thinks that it is now EVEN MORE CONSISTANT with a “Starkiller Base” analog in the process of charging up than with a Dyson(sphere, ring, shell, swarm, or WHATEVER)!

        • ljk August 9, 2016, 14:26

          You mean one of these:


          Granted, they would be great at pushing lightsail probes all across the galaxy, assuming that is what they actually built such a Dyson Swarm for.

          However, as so many humans just love to use their unsavory history as an analogy for alien thought and behavior, remember the first uses for rockets for centuries were not to peacefully explore space for scientific knowledge or just send mail across a continent, but to blow each other to bits with bigger and bigger bombs riding on top.

          That’s how the modern Space Age got its start after all. No government would have spent so much money and resources just for science, then or now.

          But hey, swords into plowshares and all that.

          • Harry R Ray August 9, 2016, 18:03

            No. I meant something like the ACTUAL “Starkiller Base” in the NEW Star Wars movie: “The Force Awakens”!!!

            • ljk August 10, 2016, 9:25

              I know will probably sound silly talking about something from the Star Wars franchise, but I found the Starkiller Base even less plausible than the Death Star, and certainly less plausible and the Nicoll-Dyson beam concept.

              And you seem to have skipped right over the actual point I was trying to make: Namely, usually such massive projects are built for defense or offense first over anything else such as peaceful, scientific interstellar vessels. At least that’s how things work on the planet called Earth.

              And for goodness sakes, if you want to fake out your enemies, don’t publicly name your ultimate weapon something that is going to basically say what it can do, which is killing your star or cause actual death. Call it something like the Peacekeeper or the Strategic Defense Initiative, that usually distracts them long enough.

              And wow, even though I presumed the planets in the Star Wars galaxy were in separate, distant solar systems, somehow the Starkiller Base weapon beam can reach them in mere minutes –
              and they are all visible with the naked eye to boot!

              Oh and here are the plans for the Death Star, just in case…


              Apparently the Starkiller Base weapon was composed of a form of dark energy called quintessense. Oy vey…


              Someone on YouTube points out all the illogics of the Starkiller Base:


              Many Bothans were very inconvenienced getting this information to you.

              • ljk August 10, 2016, 9:28

                And I am adding this just to make my Star Wars rant complete and because I know most of the people who read and write in these comments will appreciate it:


                • Harry R Ray August 10, 2016, 13:40

                  I agree with you 100%. HOWEVER, the latest data IS more CONSISTANT with this RIDICULOUSNESS than a well-thought-out “Alien Megastructure” scenario, and that just freaks me out!

                  • ljk August 11, 2016, 10:03

                    Although I continue to have difficulty in taking the Killer Starbase concept seriously (yes I messed up the name on purpose), I do offer these possible motives for building a Dyson Swarm that can behave in a similar militaristic fashion:

                    1. If you can build a Dyson Swarm you clearly have long term and far seeing goals on an interstellar scale. You may want the galaxy to yourself or just a few similarly advanced friends. You see upcoming civilizations which you calculate may compete with you for literal space and resources down the road. You are much too “civilized” to declare open war on such species. You also realize the waste of sending troops with laser rifles all the way across the galaxy just to take out these currently inferior beings. So you fry them with your Nicoll-Dyson beam from a safe distance. No muss, no fuss.

                    2. Really advanced ETI may have really advanced enemies with similar galaxy-c0nquering goals, so one needs a really big gun.

                    3. Nothing says “Don’t Mess With Us” to the rest of the Milky Way like a weapon that can fry whole planets across many light years (Maybe this is what SETI should be searching for: Sudden energetic flashes among the Milky Way stars and in other galaxies that seem to have no “natural” basis).

                    4. They’re just a bunch of jerks.

                    The following section from this great, in-depth page about aliens gives even more plausible reasons why just because you have high technology or know astronomy does not automatically mean you are going to be nice. Though in this case it may be more like “It’s nothing personal, it’s just business.”


        • Rob Henry August 9, 2016, 21:36

          Yes, if this is a Dyson Swarm, that lack of infrared excess is hard to explain if the sunlight is being utilised within the system. I agree that our data fit would demand that is being reflected, but I hope that we can come up with a more innocuous reasons Starkiller base.

          Given that the light must be being redirected, I wonder if a change in pointing direction can explain the large dips?

          • ljk August 10, 2016, 10:36

            If aliens are truly alien from humans and advanced ones are also more advanced than us morally and ethically, then they may have other uses for Dyson Swarms/Shells/Spheres than just as a big place for organic beings to run around on the inside of or as frighteningly powerful megaweapons:


            and here:


            And even these concepts may simply show a limit to human imagination, which just a cosmic blip ago wasn’t even aware of anything past its local horizon let alone that it was on a planet.

          • Harry R Ray September 12, 2016, 9:23

            Mirrors on the star-facing side of shadow squares focusing intense light on uninhabited parts of a ringworld to constantly stabilize its orbit would do just that. See my comment below.

      • EricSECT August 12, 2016, 5:31

        Rob Henry, you stated “…If we are observing a Dyson sphere, then the rate of dimming, and the seeming acceleration of that rate imply its construction is nearing completion. Surely that would require KIC 8462852 to be half the distance or less that we currently think. ”

        I’m sorry but I don’t follow how an accelerated rate of dimming requires Tabby’s Star to be closer to us than we expect, could you please elaborate?

        • Rob Henry August 12, 2016, 18:02

          Here I was looking at the most likely reason for the accelerated dimming of the central star during the construction of a Dyson swarm. Our most important clue here is that this particular sphere has no detectable IR excess, so it is reflecting light elsewhere, rather than utilising it on site. As such the missing light is not the economy of the star system and would not be expected to follow economic growth patterns. It will almost certainly be being built by automated machines. Early in its construction, these machines could well have been self-replicating – also allowing an exponential pattern, but, by the stage at which they can produce a 20% dimming in a single century, to continue in a self-replicating phase would stealing material that would be better added to the current sphere. Add this all together, and it is most likely that such an acceleration signals it is nearing completion.

        • Rob Henry August 12, 2016, 18:15

          Oops, now that I state it I see what you mean. For my above argument a 20% dimming can only support a 25% acceleration whereas here it has doubled (remember, we always start from the baseline of the magnitude of KIC 8462852 at the start of the relevant sets of observation)

  • Paul D. August 8, 2016, 0:06

    Can we rule out the possibility that there’s something on the line of sight between this star and us that’s causing a blockage, something not near the star?

  • David rawsthorne August 8, 2016, 1:14

    I read that the values of the drops are not consistent but what if a planet(s) surrounding the star had unusual orbiting moons, such as one at 90 degrees to the plane in which the planet rotates. Could this not cause a wobbly sinewave like orbit thus blocking more or less of the light depending on its location when it passes between the sun and us, also if they were similar in size like Pluto and its moon (Just much larger) could the change be because we are not only seeing the planet(s) pass at different locations across the sun, we are also seeing between one and two planets at the same time depending on the location of the 2 as they pass.

    • Michael August 8, 2016, 10:02

      I suspect that it may be a planet around which moons are orbiting creating this debris disc and flare ups. The planet does not need to occult the star just the moon/debris which can vary due to light and tidal forces. I plugged in some values of the timings and get a rough sinusoidal pattern of around 1 to 5 days around a ~24 day period. There are quite a few moons in our solar system that have periods of a few days around our gas giants.

    • hiro August 10, 2016, 17:10

      Artificial ring(s) around some gas giant(s) for collecting anti-matter (from previous topic) orbiting >5 AU from the main star is an interesting toy model.

  • Brett Bellmore August 8, 2016, 6:16

    Do the variations in brightness have enough of a periodic component to attribute to something in orbit?

    I’m wondering if we couldn’t be watching a particularly thick and “lumpy” bit of interstellar nebula drifting between us and the star, and the phenomenon having nothing to do with the star itself.

    I suppose you could check that by looking at light curves for distant stars that happen to be close to in line with this star.

  • Harry R Ray August 8, 2016, 17:30

    I just found out that Tabby Boyajian is(or will be, when Kickstarter)teaching at the same school as Bradley Schaeffer is. I can imagine some VERY INTERESTING lunchtime cafeteria discussions going on in the near future

  • Harry R Ray August 8, 2016, 17:32

    OOPS! I meant (“when Kkickstarter is over).

  • hamilton1 August 9, 2016, 18:20

    Your CAPS lock is on there Harry, jeez…

  • Harry R Ray August 9, 2016, 19:37

    There is one research angle that I have NEVER heard or seen mentioned with KIC8462852: asteroseismology. I wonder why? Is it because the star is too far away? Is it because good data CANNOT be obtained if there is a sizeable amount of solid or gaseous material BETWEEN us and the star? Is it because the M dwarf star is too close to KIC8462852 in the viewing field and would POLLUTE the data from KIC8462852 ITSELF? The reason I ask this is, IF NONE OF THE ABOVE ARE TRUE, asteroseismological data SHOULD be able to DIFFERENTIATE between starlight being BLOCKED by an outside source(comets or Alien Megastructures), energy from the star being DRAINED at or near the SURFACE of the star by an outside source(“Starkiller Base” analog)or visible light being PREVENTED from reaching the surface of the star(Dirk Bontes, theory).

  • Paul Scott Anderson August 9, 2016, 23:34

    It will be interesting to see the Gaia results re the star’s actual distance, in about five weeks. 🙂

  • Tom Mazanec August 10, 2016, 21:41

    Mr. Ray:
    Please, your capitalization pattern is hurting my eyes.

  • ljk August 15, 2016, 9:49

    A nice refresher summary of the current state of things with Tabby’s Star from this popular astronomy site, good for those who need it or need to explain to friends who have heard things but not the details:


    Just be forewarned that they tend to stick with the original view on Dyson Swarms/Shells as individual habitats occupied by organics:


    A much more progressive list of possibilities here:


  • ljk August 16, 2016, 8:51

    Tabby’s star drama continues

    Slow fading as well as sharp drops in light baffle astronomers

    By Christopher Crockett

    3:39 pm, August 15, 2016

    A star that made headlines for its bizarre behavior has got one more mystery for astronomers to ponder.

    Tabby’s star, also known as KIC 8462852, has been inexplicably flickering and fading. The Kepler Space Telescope caught two dramatic drops in light — by up to 22 percent — spaced nearly two years apart. Photographs from other telescopes dating back to 1890 show that the star also faded by roughly 20 percent over much of the last century. Possible explanations for the behavior range from mundane comet swarms to fantastical alien engineering projects (SN Online: 2/2/16).

    A new analysis of data from Kepler, NASA’s premier planet hunter, shows that Tabby’s star steadily darkened throughout the telescope’s primary four-year mission. That’s in addition to the abrupt flickers already seen during the same time period. Over the first 1,100 days, the star dimmed by nearly 1 percent. Then the light dropped another 2.5 percent over the following six months before leveling off during the mission’s final 200 days.

    Astronomers Benjamin Montet of Caltech and Josh Simon of the Observatories of the Carnegie Institution of Washington in Pasadena, Calif., report the findings online August 4 at arXiv.org: http://arxiv.org/abs/1608.01316

    The new data support a previous claim that the star faded between 1890 and 1989, a claim that some researchers questioned. “It’s just getting stranger,” says Jason Wright, an astronomer at Penn State University. “This is a third way in which the star is weird. Not only is it getting dimmer, it’s doing so at different rates.”

    Full article here:


    To quote:

    Given the star’s unpredictable nature, astronomers need constant vigilance to solve this mystery. The American Association of Variable Star Observers is working with amateur astronomers to gather continuous data from backyard telescopes around the globe.

    Boyajian and colleagues are preparing to monitor KIC 8462852 with the Las Cumbres Observatory Global Telescope Network, a worldwide web of telescopes that can keep an incessant eye on the star. “At this point, that’s the only thing that’s going to help us figure out what it is,” she says.

  • ljk August 19, 2016, 9:24

    Astronomer David Kipping gives his take on Tabby’s Star and alien megastructures:


  • ljk August 23, 2016, 8:48

    Alien Megastructure? ‘Tabby’s Star’ Continues to Baffle Scientists

    By Mike Wall, Space.com Senior Writer | August 22, 2016 07:00 am ET

    Nearly a year after first making headlines around the world, “Tabby’s star” is still guarding its secrets.

    In September 2015, a team led by Yale University astronomer Tabetha Boyajian announced that a star about 1,500 light-years from Earth called KIC 8462852 had dimmed oddly and dramatically several times over the past few years.

    These dimming events, which were detected by NASA’s planet-hunting Kepler space telescope, were far too substantial to be caused by an orbiting planet, scientists said. (In one case, 22 percent of the star’s light was blocked. For comparison, when huge Jupiter crosses the sun’s face, the result is a dimming of just 1 percent or so.)

    Full article here:


    To quote:

    Whatever is blocking the starlight from Tabby’s star is “not surrounding the whole star — it must be along our line of sight,” Wright said. “So you can do that if it’s in a disk of some kind. And that hopefully will help constrain what the heck is going on.”

    Wright has a hunch that the answer lies far away from Tabby’s star, out in the dark depths of space.

    “I think I’ve all but abandoned circumstellar explanations, and I think now we’re going to have to talk about [some] bizarre structure in the interstellar medium, and stuff like that,” he said.

    Still, Wright hasn’t given up on the alien-megastructure hypothesis. While the lack of waste heat is “almost a fatal blow” for the idea, he said, it’s still viable if the purported aliens are doing something with the waste heat — turning it into matter, for example, or converting the heat into radio waves for communication purposes.

    Astronomers have already searched for such signals coming from Tabby’s star using the Allen Telescope Array, a network of radio dishes in northern California operated by the SETI Institute. They found nothing. But Wright and his colleagues plan to conduct another search beginning in October; they’ve secured time on West Virginia’s huge Green Bank Telescope for this purpose.

    “This is a 1-in-300,000 object,” Wright said. “People have gone looking for more, and it’s the only one. So that also says you’re allowed to invoke one really rare thing, because it is a rare phenomenon.”

    [Conducting a SETI program at Tabby’s Star for a mere few weeks and declaring no aliens is not doing real science. TS should be monitored 24/7.]

  • ljk August 23, 2016, 10:20

    A nice big up-to-date take on Tabby’s Star from Next Big Future:


    To quote:

    All would agree that the absence of any infrared excess comparable to the visible flux intercepted by the occulting objects would be no mystery if the interceding objects were perfect mirrors and the stellar flux was merely being redirected out into space. But why would aliens go to such lengths just to do that? I suggest that it is the natural prerequisite for practicing large scale interstellar travel in the manner God and nature apparently intended.

    Just imagine that, despite their size, these mirrors can be shaped to optical quality. What is the diffraction limit on what a telescope with a primary mirror more than half the diameter of our sun (I estimate D~ 8e8m to cause of 22% dip) can resolve in visible light (~5e-7m)? Somewhere on the order of 1e-16 radians. Since a parsec is 3e16 meters that means they could resolve objects on the order of 10’s of kilometers on Earth when viewed from 454 pc. So, great for astronomy.

    Now assume that a similar size mirror is placed close to the star’s surface and shaped to redirect the spreading rays it intercepts into parallel rays bounced past the limb of the star. The beam would have an intensity comparable to the surface of a 6750 K blackbody, a diameter about equal to that of our Moon’s orbit, and would spread out due to diffraction by only 50 km more after traveling 1500 light years, so still a beam with the intensity of a star’s surface. Yes, that makes us pretty vulnerable if they should choose to aim the beam mirror rather than the telescope version at Earth, but that discussion is for another article (“How I Learned to Stop Worrying and Love the Mega Mirror” in which I describe my initial ‘discomfort’ before discovering that a form of deterrence should hold, given the 3000 year delay in their knowledge of technological state, and the reasonableness of any planet copying their technology to equip the guidance AI with instructions to fire back at the attacking system continually for the rest of of its’ functional life if an external beam should wipe out the home planet. I do not think mirrors responsible for the ‘Fermi paradox’).

  • ljk August 23, 2016, 17:14

    The Breakthrough Initiative – Listen and Megastructures at KIC 8463 – Andrew Siemion (SETI Talks)

    Published on March 4, 2016

    Dr. Andrew Siemion, Director of the Berkeley SETI Research Center (BSRC) at the University of California, Berkeley, will present an overview of the Breakthrough Listen Initiative, 100-million-dollar, 10-year search for extraterrestrial intelligence. Dr. Siemion will also discuss other SETI efforts ongoing at the BSRC, including the successful citizen science project SETI@Home, as well as a concerted effort to undertake panchromatic observations of the mysterious Kepler star KIC 8462852


  • ljk August 23, 2016, 17:16

    Frontiers in Artifact SETI: Waste Heat, Alien Megastructures & Tabby’s Star – Jason Wright (ST 2016)

    Published on August 12, 2016

    In 1960 two seminal papers in SETI were published, providing two visions for SETI. Giuseppe Cocconi and Philip Morrison’s proposed detecting deliberate radio signals (“communication SETI”), while Freeman Dyson (“artifact SETI”), proposed detecting the inevitable effects of massive energy supplies and artifacts on their surroundings. While communication SETI has now had several career-long practitioners, artifact SETI has, until recently, not been a vibrant field of study.

    The launch of the Kepler and WISE satellites have greatly renewed interest in the field, however, and the recent Breakthrough Listen Initiative has provided new motivation for finding good targets for communication SETI. Dr. Wright will discuss the progress of the Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies, including its justification and motivation, waste heat search strategy and first results, and the framework for a search for megastructures via transit light curves. The last of these led to the identification of KIC 8462852 (a.k.a. “Tabby’s Star”) as a candidate ETI host. This star, discovered by Boyajian and the Zooniverse Planet Hunters, exhibits several apparently unique and so-far unexplained photometric properties, and continues to confound natural explanation.


  • Tom Mazanec August 27, 2016, 17:46

    Next Big Future speculates that hypergiant mirrors may be source of dimmings http://www.nextbigfuture.com/2016/08/tabby-star-abnormalities-in-dimming-are.html

  • Harry R Ray August 29, 2016, 18:04

    I don’t know if this is pertinent or not, but what the heck. EPIC204278916: The first star even REMOTELY SIMILAR to KIC8462852, BUT: It is Known to have a disk of dusty material around it, so collisions of large planetessimals are in the mix as a potential solution. So much depends on the COMPLETE UNIQUENESS of KIC8462852 as a potential SETI candidate without confermation via detection of non-natural signals that ANY similarity with any other KNOWN star calls its validity as a site of extra-terrestrial activity into question.

    • EricSECT August 30, 2016, 7:03

      It’s pertinent!
      Can you provide us a link(s)?
      First off, I’m wondering what is EPIC-whatever doing in infrared….? And what other similarities there might be between the two stars.

  • Harry R Ray August 30, 2016, 9:46

    http://mnras.oxfordjournals.org/…/mnras.st… BUT, if you go to http://www.phys.org AS SOON AS YOU READ THIS, there is a GREAT GRAPH! The VERY BEGINNING(left side)of the graph looks STUNNINGLY SIMILAR to the very END(right side) of the KIC8462852 graph. However, there is nothing even REMOTELY RESEMBLING the “Q8” from the KIC8462852 graph, which is what I am holding out SOME HOPE for being of NON-NATURAL origin.

  • Paul Carr August 30, 2016, 10:00

    I’m pretty sure he’s referring to this: “The peculiar dipping events in the disk-bearing young-stellar object EPIC 204278916”

    • ljk September 9, 2016, 9:15

      Yes and Jason Wright has been emphasizing that this EPIC system is *not* the same as Tabby’s Star.

      Dr. Wright had this to say about the so-called second Dyson Sphere near the end of Part 9 of his series:


      “It’s an ordinary “dipper”. There are “dipper” stars that have superficially similar light curves to Boyajian’s Star. But these as caused by close-in disks and other circumstellar debris that are revealed by their long-wavelength emission, which Boyajian’s Star lacks. That was the original reason Boyajian’s Star stood out as being so weird: it’s not young, it has no disk, so it’s not a dipper. I don’t understand why this one keeps coming up.”

      Speaking of F class stars, here is an article on the subject in relation to their being places for life:


      Here is a recent article about new findings in a debris disk around an F class star:


  • ljk August 31, 2016, 11:00


    Alien megastructure ‘discovery’: a review of the facts

    Features Space 31 August 2016

    Two recent stories suggest extraterrestrial life is alive and well – and advanced enough to build gargantuan objects that we can detect. The idea is certainly tantalising, but should we take it seriously? Cathal O’Connell reports.

    Have we discovered alien intelligence? It’s the kind of story to make you giddy – like a kid who hears Santa Claus scrabbling on the roof.

    Two stories have recently toed the line between science and science fiction – but should we take them seriously?

    Here’s what you need to know.

    Have we detected an alien radio signal from a star 94 light-years away?

    Almost certainly not.

    In May 2015 astronomers detected a strong, high-frequency radio signal from HD 164595 (a sun-like star in the constellation Hercules, about 94 light years away), according to a presentation by the Italian astronomer Claudio Maccone due to be given at the International Astronomical Meeting in Mexico next month.

    At first glance, the signal seems just what the Search for Extra-Terrestrial Intelligence (SETI) Institute has been searching for.

    But alas, the signal is almost certainly not of alien origin.

    The signal has not been detected since. And when SETI pointed the Allen Telescope Array at the star over the weekend, it detected nothing.

    Second, the signal is almost unbelievably strong. To reach us at this strength, an alien civilisation would have had to blast it directly at us with a power of 50 trillion watts (equivalent to humanity’s entire energy usage at any moment).

    Meanwhile, if it was a general broadcast in all directions, it would need about 100 million times more energy than even that. That sort of wanton energy use seems unlikely, even for an advanced civilisation.

    So what was it?

    Perhaps a mundane signal was magnified to huge proportions by gravity, just like a magnifying glass can focus sunlight to melt tar. Or perhaps the signal arose with something manmade, picked up mistakenly by the Russian detector. Until the signal reappears, we may never know (and until it reappears, it’s probably not worth worrying about).
    Have we discovered an alien megastructure?

    Probably not.

    In October last year, astronomers at Yale University led by Tabetha Boyajian described a star so weird they began to call it the “most mysterious star in the galaxy.”

    The star KIC 8462852 (also known as Tabby’s star, or the WTF star) is a bigger and hotter version of our sun, though at 1,480 light-years away is too dim to see with the naked eye.

    KIC 8462852 was one of 150,000 stars monitored by the Kepler space telescope between 2009 and 2013. Kepler is a planet-hunting telescope designed to look for periodic dips in brightness as a planet passes in front of its host star, blocking some of its light.

    In 2011 and again in 2013, KIC 8462852 dimmed by as much as 20%, suggesting something huge might be in passing across the star. (Even a planet as large as Jupiter would only block about 1% of the light.)

    Whatever was blocking the light was huge – possibly half the width of the star itself.

    But more evidence from Kepler suggests the shadows are cast by many irregularly shaped objects passing across the face of the star, rather than one large one.
    Natural explanations

    Boyajian’s team and other astronomers have proposed many different possible explanations for this behaviour.

    They’ve concluded, for example, that KIC 8462852 is not the kind of star that naturally varies in brightness.

    Another explanation might be that the star has a very busy solar system, with dust, disks or protoplanets ganging around. But such solar systems typically envelop very young stars. KIC 8462852 has the appearance of a mature star and is not in a star-forming region.

    The most favoured natural explanation, as proposed by Boyajian and developed by others, is probably that the dimmings are caused by a family of comets passing in front of the star. This family would have originated as a single comet, which was ripped apart after a close encounter with a large planet, or the star itself.
    Unnatural speculation

    But another explanation, which has still not been ruled out, is that the star is enveloped by an alien construction project of extraordinary proportions.

    The idea was proposed by Jason Wright, an astronomer at Pennsylvania State University. “Aliens should always be the very last hypothesis you consider,” he told The Atlantic, “but this looked like something you would expect an alien civilisation to build.”

    The structure we’re talking about here would be something like a Dyson sphere – built from millions of solar panels in orbit around a star and making use of almost all of a star’s energy output.

    The idea was first described in the 1930s sci-fi epic Star Maker, and popularised in 1960 when the English-born American physicist Freeman Dyson explored the idea in more detail.

    A study led by Wright concluded that the KIC 8462852 signal has “all of the hallmarks” of a Dyson sphere.

    Attributing the signal to a giant alien construction project is certainly tempting. After all, with astronomers estimating there are about 40 billion potentially habitable planets in our galaxy, it’s something of a mystery why decades of SETI searches have so far proved fruitless.

    But on the other hand, the data doesn’t fit the Dyson sphere idea too well either.

    The problem boils down to thermodynamics. Inevitably, some of the energy harnessed by a Dyson sphere would be emitted as waste heat.

    In Dyson’s original 1960 paper, he suggested looking for sources of this waste heat as part of a search for extraterrestrial intelligence.

    But Tabby’s star doesn’t seem to emit this radiation. And SETI scientists searching for radio signals from the star have also come up with nothing.

    From the “canals” on Mars in the late 19th to the periodic LGM-1 (“Little Green Men”) signal of the 1960s, astronomers have often attributed mysterious phenomena to intelligent beings. Yet these explanations have been replaced by something altogether more mundane.

    The supposed canals turned out to be optical illusions, while the LGM signal is now recognised as a pulsar (a kind of star that rapidly spins emitted light like a lighthouse).

    Perhaps these explanations come about from our tendency to credit structure to a creator. Perhaps they come from wishful thinking – after all, who hasn’t stared at the stars and wondered?

    Or perhaps they simply come from a failure of our imagination. As Boyajian says: “One thing for sure is that nature has a much better imagination than we do.”

  • ljk August 31, 2016, 11:09


    Astronomy and meta-Astronomy by Jason Wright

    What Could Be Going on with Boyajian’s Star? Part I


    What Could Be Going on with Boyajian’s Star? Part II


    • EricSECT September 1, 2016, 14:53

      An edge on ring…. seems to work as it explains the long term and short term dimmings along with the lack of excess IR…. BUT…. considering that the star’s pole is tipped to our line of sight about 70 degrees, then this disk is not in orbit around Tabby’s equator. Is that even stable? The star spins fast, 0.88 days and must have an equatorial bulge. Tidal forces from this bulge should force the disc, no matter where or how it formed, into an equatorial orbit, and no longer edge on to us.

      Perhaps this off-axis ring is stable for, lets say, 1 billion years? Maybe then…. we have the star’s age wrong, it’s not middle aged but very young. A left over accretion disc, maybe even forming planets, etc.

      • ljk September 6, 2016, 12:37

        I know Dr. Wright is referring to a natural ring system, however I cannot help but think of Larry Niven’s Ringworld and how it was called out as inherently unstable early on.

        Quoting from here:



        A ringworld design requires active stabilization, because it is not in inertial orbit. Though the ring itself is rotating at 1200 km/s (to approximate Earth gravity), the center of mass is stationary — in fact, it is at an unstable equilibrium, roughly comparable to a small sphere balanced on top of a larger one.

        Thus, large thrusters must be incorporated into the design to keep it centered about its star. This point gave Niven some difficulty after he published his first Ringworld novel; he was deluged with letters pointing out that “the Ringworld isn’t stable” and dedicated the first sequel to a resolution of this problem. He notes in the dedication of Ringworld Engineers that at the 1971 World Science Fiction Convention MIT students crowded the hotel hallways chanting “The Ringworld is Unstable!” In this first sequel, he also tackled how to prevent all the soil from ending up in the oceans. In the fourth book in the series, Ringworld’s Children, he creates backplot explanations for several of the imperfections in his original design of the Ringworld — and wholly glosses over others, such as that Louis Wu is worried about his dietary intake of salt since only the Great Oceans are described as being saline.

        • EricSECT September 6, 2016, 16:06

          In essence:
          A Niven ring, off polar axis, is not stable.
          Unless it is very far away from the star.

          The best possible construction would have some kind of a passive defense to protect from being unstable.

          • Harry R Ray September 6, 2016, 19:51

            Perhaps what we are seeing here is NOT the MAIN ringworld structure itself(which, in this case would NOT transit the star),but, INSTEAD; the SHADOW SQUARES! In that case, theSTAR-FACING sides of the shadow squares would be MEGA-MIRRORS which would FOCUS starlight onto UNINHABITED sections of the main structure to PUSH the main structure AROUND in a way that provides this “passive defense”. This would ALSO mean that the shadow squares themselves do not build up any kind of HEAT in their structures, thus rendering NO IR SIGNAL!

            • ljk September 9, 2016, 9:28

              Tom M. posted the following link above in this thread regarding megamirrors, which could also be shadow squares:


              Again, how does one keep them stable? What materials do you use to have them handle all that solar radiation and yet not glow in the infrared? Please do not say they are made of magic alien handwavium.


              • Harry R Ray September 12, 2016, 9:32

                I’m not saying NO HEAT WHASOEVER, but; if a mega-mirror REFLECTS 99.99(99?)% of the star’s optical light, that leaves only a smidgen to be CONVERTED into IR! Add on whatever IR the star is prodicing and spread the TOTAL over the ENTIRE Earth-facing exterior of a GINORMUS shadow-square and NONE of our current instruments(save for ALMA, which CANNOT OBSERVE KIC8462852)! JWST MAY be able to detect this IR when it is launched!

  • ljk August 31, 2016, 16:53

    What Could Be Going on with Boyajian’s Star? Part III: Periodic(?) Dips and Interstellar(?) Sodium


    What Could Be Going on with Boyajian’s Star? Part IV: Nearby Stars, Instrumental Effects, and a Solar System Cloud


  • ljk September 1, 2016, 10:10

    What Could Be Going on with Boyajian’s Star? Part V: The Interstellar Medium


  • ljk September 1, 2016, 13:48
    • EricSECT September 1, 2016, 14:38

      A good summary of the status of the apparatus by Dr. Wright.

      I hope he includes a chapter on possible astrophysical causes, intrinsic to “F” stars like Tabby’s , stars that may be about to exit the main sequence and are in an instability region.

      • ljk September 6, 2016, 12:28

        I am posting the rest of the series now. See below in this thread.

        • EricSECT September 6, 2016, 16:09

          Dr Wright gave an excellent summary but I am disappointed that in this intrinsic variations section, the uncertainties in the determination of Tabby’s age was not discussed. This uncertainty could place Tabby’s close to exiting the main sequence and thus be the cause of it’s weirdness.

          Age determination for individual stars like Tabby’s is a calculated value. Things that can be measured (color, apparent brightness, metallicity, temperature-indirectly) get input into computer models. The star is then classified “F” etc. An age value gets spit out of computer models (with inherent uncertainties as it is a calculated value) based on theoretical model(s) for “F” stars. These theoretical models COULD require some tweaking. If the calculated value for age uncertainty is +/-30%, then for an F class star whose life expectancy is about 3 billion years, there is a non-negligible chance the star is at end of MS life.

  • ljk September 6, 2016, 12:42

    Parts 7 through 10 linked here:

    What Could Be Going on with Boyajian’s Star? Part VII: Circumstellar Dust


    What Could Be Going on with Boyajian’s Star? Part VIII: Alien Megastrutures


    What Could Be Going on with Boyajian’s Star? Part IX: Intrinsic Variations


    What Could Be Going on with Boyajian’s Star? Part X: Wrapup and Gaia’s Promise


  • ljk September 6, 2016, 13:09

    On September 2, 2016, there was a popular news item about astronomers finding a second Dyson Sphere type star system:


    Turns out it is not like KIC 8462852 in several key ways, but again, you can see in the article the almost desperate need to explain Tabby’s Star as a natural phenomenon – ANY natural phenomenon, please Dear Lord – just not the A word (or the E word, or the M word).

    No, I do not subscribe to shouting ALIENS whenever something new and strange is discovered in the Cosmos. There is plenty we humans have yet to learn about the vast reality around us and so far there seems to be little that cannot be explained by non-intelligent actions.

    Except KIC 8462852.

    Jason Wright has deftly shown in a ten-part series answering just about every idea as to what Tabby’s Star could be, and gosh darn it if that strange thing way out there in the galaxy doesn’t match up precisely with what we know. And no, maybe it is not due to aliens, but isn’t it time in 2016 to stop shying away as if this were just about any earlier era in human history?

    Even if there isn’t so much as an alien microbe out there, the real Universe that we know through science – the one that is 13.7 billion years old and holding at least 100 billion galaxies (and I will refrain from the possibility of infinite other universes for the moment) – has clearly shown that humanity and Earth are not the focal point of existence. So let us stop acting like we are all that and that our ideas are solid and ultimate. Remember, we are the species that less than a century ago was still debating whether the Milky Way galaxy was the only such stellar island in the Cosmos or just one of many. Less than one century ago.

    Dr. Wright had this to say about the so-called second Dyson Sphere near the end of Part 9 of his series:

    It’s an ordinary “dipper”. There are “dipper” stars that have superficially similar light curves to Boyajian’s Star. But these as caused by close-in disks and other circumstellar debris that are revealed by their long-wavelength emission, which Boyajian’s Star lacks. That was the original reason Boyajian’s Star stood out as being so weird: it’s not young, it has no disk, so it’s not a dipper. I don’t understand why this one keeps coming up.

  • Paul Carr September 9, 2016, 13:59

    If the mirrors (possibly millions of them) are floating on the starlight, and are highly efficient, and the backs of the mirrors are not facing us, they would barely observable in the IR, or maybe not at all.

    Of course, we have no technology here on Earth that can do anything like that, but it’s not impossible in principle.

    My own 2 cents on the mirror idea: https://disownedsky.blogspot.com/2016/09/almost-certainly-wrong-alien.html

    We could be looking at a side lobe in this scenario.

  • Harry R Ray September 14, 2016, 11:07

    You saw it here FIRST: David Hippke just tweeted “Tabby’s Star’s distance is 392(+50-40)PC”. so 1480 light years IS in the error box, but it is likely to be SOMEWHAT closer, but NOT NEARLY AS CLOSE as my thought experiment predicted, THUS: The dimmind MUST HAVE STARTED in only a reasonably short time BEFORE 1890!

    • Harry R Ray September 20, 2016, 9:40

      CORRECTION(maybe): “Evidence for a systematic offset of -0.25 mas in the Gaia DR1 paralaxes.” by Keivan G Stassun, Guillermo Torres. ArXiv:1609.05390(…distances too long…)! That would mean that the ACTUAL highest probability distance would be <300 light years, and that the TRUE paralax being in the LOWER END(i.e. 1.2 sigma) of the error box WOULD BE CONSISTANT(ONLY 1.2 sigma, though)with my thought experiment AFTER ALL!

      • ljk September 30, 2016, 14:12


        A first view with GAIA on KIC 8462852 – distance estimates and a comparison to other F stars

        Michael Hippke, Daniel Angerhausen

        (Submitted on 18 Sep 2016)

        Distance estimates from Gaia parallax and expected luminosities are compared for KIC 8462852. Gaia DR1 yields a parallax of 2.55±0.31mas, that is a distance of 391.4+53.6−42.0pc, or 391.4+122.1−75.2pc including systematic uncertainty. The distance estimate based on the absolute magnitude of an F3V star and measured reddening is ∼454±35pc. Both estimates agree within <1σ, which only excludes some of the most extreme theorized scenarios for KIC 8462852.

        Future Gaia data releases will determine the distance to within 1% and thus allow for the determination a precise absolute luminosity.

        Comments: Comments welcome

        Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

        Cite as: arXiv:1609.05492 [astro-ph.SR]
        (or arXiv:1609.05492v1 [astro-ph.SR] for this version)

        Submission history

        From: Michael Hippke [view email]

        [v1] Sun, 18 Sep 2016 14:22:23 GMT (394kb,D)


  • Harry R Ray September 16, 2016, 9:35

    OOPS: I meant Michael Hippke.

  • EricSECT September 17, 2016, 6:43

    Does anyone know what year (say, 1900AD) that Tabby’s Star’s distance was officially calculated by apparent magnitude? Because if it was at around 1900 AD, then that roughly correlates with and confirms Brad Schaffer’s dimming trend.

    • Paul Carr September 17, 2016, 11:47

      The eraliest catalig I am aware ic iz thw USNO-B1.0, based on images taken in 1950 at Palomar.

  • EricSECT September 18, 2016, 5:18

    Thanks, Paul.
    Still supports Shaeffer, although perhaps then more of an exponential trend in dimming instead of a linear trend? The final nail in the coffin would be validation by those Sonnenberg plates, have they ever been scrutinized?

  • Jim Strom September 19, 2016, 15:06

    I know KIC 8462852 is of interest to C-D’s readers:


    Conclusion: “I have proposed a type of model that is mathematically simple and, with slight variations, is able to produce excellent fits for all the major brightness drops observed in Tabby’s star. If this is the correct type of model — its goodness of fit is highly encouraging — the following hypotheses should be considered: [Niven ring], [Dyson swarm], or [early stage accretion disk]”.

    • Harry R Ray September 19, 2016, 19:25

      Jim Strom and Dirk Bontes.Sorry, your theories don’t work anymore!!! HERE’S THE LATEST: Centroid is OFFSET for the smaller dips, but NOT for the LARGER ONES!!! This can ONLY MEAN that whatever is CAUSING the dipping is causing TWO STARS TO DIP SIMULTANEOUSLY!!!!!! THEREFORE: What we know as KIC8462852 is ACTUALLY Boyajian’s Star AND a “blend” star SOMEWHERE BETWEEN US AND BOYAJIAN’S STAR!!! If the ‘blend’ star is NOT PHYSICALLY associated with Boyajian’s Star, this COMPLETELY ELIMINATES Alien Megastructures. That means a non-natural solution can be true IF AND ONLY IF they are a very wide period binary in precicely the right configuration! Then, AND ONLY THEN would we be seeing TWO megastrucrures, one 99% completed(the “blend”star, the other(Boyajian’s Star) only PARTIALLY completed!!!

  • EricSECT September 19, 2016, 17:01

    Supposedly, Tabby’s poles are tipped to our line of site 70 degrees (+/- 20 degrees). Does anyone know how they make this determination?

    Anything in orbit, natural (accretion disc) or un-natural no matter where it initially starts off will be dragged into an orbit about the star’s equator due to tidal forces. It is not passively stable.

    I don’t see Jose Solorzano’s models taking the 70 degree tilt into consideration.

  • ScottAnthony September 22, 2016, 23:44

    I mentioned it once and actually wasn’t kidding: so-called quantum entanglement. In case nobody has noticed, the cat is in the bird. “They” may be showing us their sense of humour, if so that seems pretty awesomely positive to me.

    The future is a path through clouds of probability, every act by every object generating “probability futures.” at least theoretically advanced enough knowledge enables “choosing” of this or that path (as desired, presumably) If this is “true,” then “they” are “here” already – within every single atom of the planet, which of course includes all Her biota.


    In the reality version, so far in our development we don’t even know the existence of “tusks,” or “feet,” or “probosces” yet. everyone’s clustered around feeling the tail discovery (quantum mechanics, astrophysics, etc), i.e. “It’s a curtain pull!” … “It’s a mop-head!”…:Dreadlocks! Run!” and etc. Imagine being perhaps thousands of years (by our measurement) more advanced into the never-ending wonders. I believe that, then, “they” (who I wouldn’t be surprised look a lot like us! Or at least can if they want!) In this scenario, a very smart and very curious woman whose name is Tabitha was at some point in her life very gently and very graciously “nudged” into a probability vector of “future possibilities” – hey, who knows, maybe some little choice she made when she was 4 years old! – and which she, with her own intelligent free-will then followed right to the present day – I repeat: the cat is in the bird!

    I chose the tail for a specific reason. Can you guess it.

  • ljk September 30, 2016, 14:08


    Sonneberg plate photometry in two colors for KIC 8462852: No dimming between 1934 and 1995

    Michael Hippke, Peter Kroll, Frank Matthei, Daniel Angerhausen, Taavi Tuvikene, Keivan G. Stassun, Elena Roshchina, Tatyana Vasileva, Igor Izmailov, Michael B. Lund

    (Submitted on 29 Sep 2016)

    The F3 main sequence star KIC 8462852 has raised interest because of its mysterious day-long brightness dips, and an unusual ~3% brightness decrease during the 4 years of the Kepler mission.

    Recently, a 0.164mag (~14%) dimming between 1890 and 1990 was claimed, based on the analysis of photographic plates, although this has been refuted.

    To resolve this controversy, we have gathered an independent set of historic data from Sonneberg Observatory, Germany. From these historic plates, we could extract 862 magnitudes in blue light, and 401 magnitudes in red light. The data cover the years 1934 to 1995 and are very evenly sampled between 1956 and 1995.

    In both colors, we find the star to be of constant brightness within 0.033mag/century (~3%). The previously claimed dimming is inconsistent with these data at the ∼5σ-level, however the recently reported modest dimming of ~3% in the Kepler data is not inconsistent with these data. We have also searched for periodicities and yearly trends in the data and find none within our limits of ~10% per year.

    Comments: Comments welcome

    Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

    Cite as: arXiv:1609.09290 [astro-ph.SR]
    (or arXiv:1609.09290v1 [astro-ph.SR] for this version)

    Submission history

    From: Michael Hippke [view email]

    [v1] Thu, 29 Sep 2016 10:29:11 GMT (2912kb,D)


  • ljk September 30, 2016, 14:13


    A first view with GAIA on KIC 8462852 – distance estimates and a comparison to other F stars

    Michael Hippke, Daniel Angerhausen

    (Submitted on 18 Sep 2016)

    Distance estimates from Gaia parallax and expected luminosities are compared for KIC 8462852. Gaia DR1 yields a parallax of 2.55±0.31mas, that is a distance of 391.4+53.6−42.0pc, or 391.4+122.1−75.2pc including systematic uncertainty. The distance estimate based on the absolute magnitude of an F3V star and measured reddening is ∼454±35pc. Both estimates agree within <1σ, which only excludes some of the most extreme theorized scenarios for KIC 8462852.

    Future Gaia data releases will determine the distance to within 1% and thus allow for the determination a precise absolute luminosity.

    Comments: Comments welcome

    Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

    Cite as: arXiv:1609.05492 [astro-ph.SR]
    (or arXiv:1609.05492v1 [astro-ph.SR] for this version)

    Submission history

    From: Michael Hippke [view email]

    [v1] Sun, 18 Sep 2016 14:22:23 GMT (394kb,D)


  • ljk October 3, 2016, 13:51

    Our galaxy’s most-mysterious star is even stranger than astronomers thought

    Monday, October 03, 2016

    Pasadena, CA— A star known by the unassuming name of KIC 8462852 in the constellation Cygnus has been raising eyebrows both in and outside of the scientific community for the past year. In 2015 a team of astronomers announced that the star underwent a series of very brief, non-periodic dimming events while it was being monitored by NASA’s Kepler space telescope, and no one could quite figure out what caused them. A new study from Carnegie’s Josh Simon and Caltech’s Ben Montet has deepened the mystery.

    Simon and Montet’s findings caused a stir in August, when they were posted on a preprint server while their paper was being reviewed. Now their work is now accepted for publication by The Astrophysical Journal.

    Full article here:


    To quote:

    “The steady brightness change in KIC 8462852 is pretty astounding,” said Montet. “Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time. It is unprecedented for this type of star to slowly fade for years, and we don’t see anything else like it in the Kepler data.”

    “This star was already completely unique because of its sporadic dimming episodes. But now we see that it has other features that are just as strange, both slowly dimming for almost three years and then suddenly getting fainter much more rapidly,” Simon added.

    Astronomers were already running short of good ideas to account for the dips in KIC 8462852’s brightness, and the new results will make that task even harder. Simon and Montet think that the best proposal so far for explaining the star’s drastic six month dimming might be a collision or breakup of a planet or comet in the star’s system, creating a short-term cloud of dust and debris that blocks some starlight. However, this wouldn’t explain the longer-term dimming observed during the first three years of Kepler and suggested by measurements of the star dating back to the nineteenth century.

    “It’s a big challenge to come up with a good explanation for a star doing three different things that have never been seen before,” Montet said. “But these observations will provide an important clue to solving the mystery of KIC 8462852.”