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Bradley Schaefer: A Response to Michael Hippke

The question of a gradual dimming of KIC 8462852 continues to make waves, the most recent response being Michael Hippke’s preprint on the arXiv site, discussed in the post immediately below. Bradley Schaefer (Lousiana State University), who published his work on the dimming he found in now digitized photographs in the archives of Harvard College Observatory, disagrees strongly with Hippke’s findings and is concerned that the paper impugns the solid work being performed by DASCH (Digital Access to a Sky Century@Harvard). Below is Dr. Schaefer’s response with details on the astrophotographic photometry at the heart of the issue.

by Bradley E. Schaefer

schaefer

A few hours ago, Michael Hippke posted a manuscript to arXiv (http://arxiv.org/abs/1601.07314), and submitted the same manuscript to the Astrophysical Journal Letters (ApJLett). This manuscript claims to have found that the DASCH data produces light curves with secular trends (both systematic dimmings and brightenings) over the century-long records. This same DASCH data (from the collection of archival sky photographs now at Harvard Observatory) was used to recognize a dimming of KIC 8462852 (a.k.a. ‘Tabby’s Star’ or the ‘WTF star’) at an average rate of 0.165±0.013 magnitudes per century from 1890 to 1989.

This dimming from the DASCH data is just a long-time scale version of the dimming also seen with the Kepler spacecraft, and these dimmings are still a high mystery and a perplexing problem. Hippke is taking his claimed result (that the majority of DASCH light curves have major and widespread calibration errors resulting in apparent secular trends) as then implying that KIC 8462852 does not have any secular trend. This claim is easily proved wrong.

Hippke made two major errors, both of which are beginner’s mistakes, and both of which will erroneously produce apparent dimmings and brightenings when none exist. First, Hippke explicitly includes red-sensitive and yellow-sensitive photographs together with the blue-sensitive photographs. The different colors will produce systematically different brightnesses (magnitudes). The trouble is further that the red and yellow photographs are predominantly at late times in the century-long light curve (in the 1970s and 1980s), so the inclusion of many magnitudes that are systematically high or low only at the end of the century will artificially make the star appear to brighten or dim over the century.

Second, Hippke explicitly includes magnitudes from photographs with known and recognized defects. The Harvard photographs are not perfect, with some having long-trailed images, some being double exposures with stars overlapping, and some having various plate defects where the emulsion is nicked or such. The DASCH scanning and software has a robust means of identifying problem photographs, and these are objective measures independent of the magnitude. These known-poor-quality magnitudes should not be used for any sensitive purposes. Colloquially put, these are ‘garbage’. Hippke keeps all the many good DASCH magnitudes and he also adds in the garbage magnitudes, so his final light curves have many points that are systematically skewed.

The frequency of the poor-quality magnitudes varies over time, usually with more early-on during the century. And the erroneous magnitudes are variously systematically brighter or dimmer, also varying over the century. The result of Hippke’s good+garbage light curves is that the garbage points tilt the light curve by a bit. This is seen when I take all of Hippke’s same stars and data and go from his sloped light curves (including his garbage points) to flat light curves (with only the good points). The bottom line is that Hippke’s second big mistake was to include the poor-quality photographs. Garbage-in, garbage-out.

So we understand why Hippke’s secular trends are wrong. But we already knew this very well anyway. The reason is that the DASCH people have already measured many (likely up around the millions) of light curves for single main sequence stars (i.e., stars that really should be perfectly constant) and found that their light curves are actually very flat. This is in stunning contradiction to the claims of Hippke that the majority show big secular trends.

Hippke’s paper has a title of “KIC 8462852 Did Likely Not Fade During the Last 100 Years”, yet his paper never discusses or analyses any data from KIC 8462852. One reason is perhaps that he cannot get around the flatness of the five check star light curves. That is, these five stars always appear within 3 millimeters of Tabby’s Star on these 10″x8″ phootgraphs, these stars are all of similar brightness as Tabby’s Star, and they all have similar color as Tabby’s Star.

If there were any systematic problems for the DASCH data with Tabby’s star, then we should see the exact same dimming trend in the check stars as is seen for Tabby’s Star. But we do not. These ‘check stars’ serve as the classic control study in science. They serve as proof that neither the check stars nor Tabby’s Star have any substantial systematic problem. They serve as proof that Hippke’s title is wrong.

Hippke submitted his draft manuscript to ApJLett, to arXiv and to reporters even before he had any checks with experts on archival sky photographs. For example, I first read his email just about the time that he was submitting his manuscript. He did not contact any of the DASCH people, despite them being the target of his attack. Indeed, he has not talked with anyone who has any experience with or knowledge of any archival photographs. This topic has a lot of detail and many quirks, but Hippke apparently did not have the realization or the will to check out his claims. And, in an email from Hippke from early this morning, he explicitly labelled himself as “a novice” for this technical topic. So he is a novice working without bothering to check with anyone knowledgeable. As such, it is not surprising that he made beginner’s blunders.

A broader problem is now that DASCH has the publicly-stated claim that it has major, widespread, persistent calibration and measurement errors. In knowledeable circles, Hippke’s paper won’t come to anything. But these circles are not large, because few people really understand the working of DASCH or plate photometry.

So most people will simply look at the paper’s conclusions, not recognize the horrible beginner’s blunders that create the false conclusion, and only come away thinking that the DASCH light curves are “wrong” or at least “questionable”. Public perceptions do matter for many aspects. Most important for DASCH is their future success rate in funding proposals, the reception of all future papers relating to DASCH, and the future useage of the DASCH data.

Perhaps from a journalistic point of view, any ‘stirring of the pot’ is good copy. But from the point of view of science and knowledge, putting up unchecked and false claims is bad all the way around. Science has a great strength of being error-correcting, with the normal procedure now for the DASCH people to put out a full formal refutation of Hippke’s claims, and such will appear in many months. But with the one-day turn-around of arXiv and with fast journalist response, there will be many months where the reputation of DASCH is maligned. So Hippke’s choice of running to reporters before the paper appeared publicly, and disdaining any experienced advice despite being a self-proclaimed “novice”, is not good science.

——-

For more on this controversy, see KIC 8462852: Where Are We After Eight Months?, Michael Hippke’s follow-up.

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Comments on this entry are closed.

  • EricSECT January 28, 2016, 18:01

    Seems pretty damning! And the neighboring stars around Tabby’s: No changes in luminosity… evidence to rule out (maybe?) at least a gigantic interstellar dust cloud causing Tabby’s dimming. Was Hippke’s paper even vetted by peers?

    • Andrew Norman January 28, 2016, 18:49

      No, I think that’s how AXIV works. You post your manuscript before it’s necessarily been vetted by anyone. Sometime after that it gets published in a peer-reviewed journal, if it’s accepted.

      • Andrew Norman January 28, 2016, 18:50

        *ArXiv

      • Eric Perlman January 29, 2016, 22:38

        While it works that way in practice, that’s not how it *should* work. This happens quite often, and is a powerful argument against posting on ArXiv before acceptance. I get yelled at for saying this, but … If you care about quality science, keep ArXiv for accepted papers only.

    • dryson February 1, 2016, 22:17

      It Can’t Be Comets – Cometary debris glows due to the interaction with the Sun and the dust and ice particles of the tail. If there had been a swarm of comets transiting across KIC for 2.5 to 5.0 days at a time, which is a very slow transit velocity for a comet given Earth transits our own Sun in 13 hours and Jupiter makes it’s transit in 33 hours, then there would have been a cometary tail that would had to have been present in order to cause the dims of KIC. The swarm of comets would have been far to small to have been picked up by Kepler. In one article it was said that over 600,000 200km in diameter comets would had to have been present to cause the dim if there was not any cometary tail. That many comets grouped together would equal a small planet still not able to be detected by Kepler or cause a dim unless it was the size of Earth or larger, larger meaning the size o Jupiter The objects transiting KIC were very slow moving. Far to slow for planet or large swarm of comets.

  • Andrew Norman January 28, 2016, 18:26

    Peer review may be laborious and imperfect, but it’s critical.

  • Frank Smith January 28, 2016, 18:27

    My money is on Schaefer…

    • Larry Kennedy January 29, 2016, 7:21

      @ Frank Smith
      Ditto

  • Rob Henry January 28, 2016, 18:41

    So were Bill’s comments on the last post a red herring (that most of Hippke’s stars were known variables, multiple stars, or non-mainsequence)?

  • Bill January 28, 2016, 18:52

    Wow, at first glance Hippke’s claim seems to be in serious trouble. Schaeffer spent a lot of time in his paper describing how he excluded various low-quality measurements, and it appears that Hippke did none of that. We really need somebody who is willing to take the published DASCH data for dozens or hundreds of nearby F-dwarfs, weeding out the bad measurements, and see what they show.

    • Massimo Marengo January 28, 2016, 20:12

      The DASCH collaboration does that routinely as part of their calibration. They derived secular light curves of a large number of photometric standard stars, and many of those are F stars. They didn’t find any trend.

      • Cyril January 29, 2016, 0:05

        Schaefer is probably angry that Hippke went to reporters before his work had been peer-reviewed. Hippke’s paper may be wrong (seems likely), and his eventual retraction may not be noticed. So he may have polluted the public consciousness with incorrect information. That is probably one reason that Schaefer is angry.

        • Matt January 29, 2016, 20:00

          “Schaefer is probably angry that Hippke went to reporters before his work had been peer-reviewed.”

          Schaefer’s paper is NOT accepted by peer review either, it is submitted to APJ Letters _just like_ Hippke’s. And he has been doing interviews, podcasts, and now open letters? Lots of irony here…

          As far as the rhetoric: ‘garbage-in, garbage-out…’, are you kidding me? Pretty disappointing to see such a meltdown from an astronomer of this caliber.

          By taking the stance that the exo-comet theory is invalidated with his single, un-vetted result, Schaefer is JUST AS GUILTY of altering public perception about this F star as Hippke, or anyone else that has gotten involved. At least the latter had the collegial integrity to actually cite the SETI paper that caused all of the international attention in the first place.

          As far as DASCH, there is nothing I saw in the Hippke print that I would construe as an attempt to malign the organization’s reputation. Hard to come away from this post with anything but the taste of bitter arrogance. WOW!

          I think it’s safe to say we need a third, and probably fourth, opinion on the plates.

          • Ashley Baldwin January 30, 2016, 14:12

            Well said Matt. I fully agree. Those of us familiar with the ” letters to the Editor” section of journals in any scientific domain (my own area of medicine being no exception) will be familiar with such things that can become nothing short of diatribe trials , but at least these will be post peer review ( and often fuelled by those very Editors , under pressure to sell copy and knowing everyone loves a good fight ) . Here there is at least a built in delay to “take a deep breath and reflect” before pressing the “submit” button too. Hippke also went out of his way to praise the methodology of the Schaefer study to be fair.
            It’s a real big thing for a layman like me to see and participate in real time ,transparent astrophysical debate. That’s exactly what a reputable site like this is all about and why so many professionals follow and contribute to it . What better a way to spread the word and let everyone know what’s happening and about all the hard work that is being put in around the world . A fantastic thing ,a perfect advert for citizen science and to opportunity to champion new developments like “pale red dot ” and such the like . A great new development where debate is fine , even disagreement, especially when “raw” . But I think it’s important for protagonists to acknowledge it is “all in the open” and cater any rebuttals / replies in recognition of this fact.

          • Volucris January 31, 2016, 12:15

            “Garbage-in, garbage-out” while not quite diplomatic language, is a widely used colloquialism in data science/statistics, etc. I wouldn’t call using it exactly a meltdown.

            • Mark Zambelli February 1, 2016, 12:00

              And used very widely in astrophotography circles… I’ve shed a tear or two over the years when I have to ditch a (hopefully low) percentage of the 6 minute sub-exposures I’ve aquired during, say, a 5 hour session for various reasons (temporary cloud, vibrations from the railway line ruining an image with the ‘squiggles’, gust of wind shook the scope, satellites cutting through faint nebulosity etc…). It’s a fine line to determine if any of the garbage would enhance in any way, or just detract from, the final stacked image (for aesthetics only though… for scientific data it would be a much bigger problem). It’s a lot easier ditching the garbage when you have an embarassment-of-riches in raw data… but when the sample is small, to err is human by including some of the lower quality data.

  • Thomas January 28, 2016, 19:12

    It sounds like Schaeffer is right, but jeez, he needs to take a chill pill. Calling Hippke’s paper an “attack” is a very overly dramatic response.

    • Larry Kennedy January 29, 2016, 7:23

      @ Thomas
      Schaeffer very clearly states why he is not being “chill”.

    • Jim Strom January 29, 2016, 13:35

      As Dr. Schaeffer mentioned, the careless critique could harm funding for important research. That makes me mad too. Hippke might or might not have some points, but only fools rush in.

  • Waiting for 4MOST January 28, 2016, 20:02

    You state they did none of this quality control cuts but it says in Hippke’s paper.

    “We note that our results remain virtually identical if data cleansing, as described by Schaefer (2016), is applied.”

    Is it beginners mistakes or has something been missed in the paper? You claim these cuts remove the trends but it’s a shame neither you nor the paper have shown this in detail.

  • Realpra1 January 28, 2016, 22:29

    Can Bradley or someone else comment on the fact that the B magnitude is now 12.82 according to data from 2000 in the SIMBAD archive?

    Does this mean the star dimmed another 18.5% for a total of ~38% since 1890?

    • Harry R Ray January 29, 2016, 10:37

      Does the “SIMBAD archive” you talk about use optical ccd images? If so, that fills in 50% of the data linking the DASCH data to the Kepler lightcurve. 38% dimming from 1890 to 2000 IMPLIES an ADDITIONAL 18% dimming from 1990 to 2000!!!! I predicted an additional dimming of ONLY 4-5% between 1990 and 2010, ASSUMING Schaefer’s linear progerssion was CONSTANT! Keep in mind, bins 4 and 5 in the Schaeffer analysis ALSO showed a MUCH GREATER DIMMING than Schaefer’s linnear progression can explain! If this is TRUE, we need the FINAL TEN YEARS(2000-2010) of data ASAP! FINALLY: to EXPAND upon my “thought experiment”, it appears that, if my “GAIA” prediction holds up, Schaeffer’s work will be TOTALLY VINDICATED and KIC 8462852 will be likely RECLASSIFIED from an F3V main sequence star to an F3IV subgiant, increasing the POSSIBILITY that the steller fluctuations ARE of INTERNAL ORIGIN!

    • Paul Carr January 29, 2016, 15:05

      Boyajian, et. al. list it as 12.262. The SIMBAD number comes from Hipparcos data – I’m not sure how good the photometry is, or what corrections are included.

      • AS Mascareño January 31, 2016, 18:14

        You should always take SIMBAD numbers with a grain of salt. It’s a great database, and incredibly useful, but the information listed is not always the best one or the most recent.

        • Harry R Ray February 3, 2016, 11:25

          MORE DATA: The Boyajian paper 12.262 mag determination was in the B band. RIGHT BELOW THAT, the V band magnitued was listed as 11.705. Hog et al had a 2000 V band listing of 12.01, which would indicate a slight brightening(instead of a slight dimming)FOR THIS BANDWIDTH ONLY. Does this have any SIGNIFIGANT meaning? Somebody help me out here, please.

          • Rafik February 4, 2016, 6:05

            To get a comparable current magnitude measurement for KIC 8462852 we need either to get contemporary set of photographic plates using the same techniques as the Harvard plates, another series of plates that overlaps the Harvard plates so we can recalibrate the measurements or take current CCD images of KIC 8462852 and a range of similar nearby stars and then compare the results with the late 1980’s measurements in the Harvard plates.

            I am sure someone must be looking at doing this work as it will answer the question that all of us have –
            Has the magnitude of KIC 8462852 dimmed, brightened or remained constant since 1989?

          • Rafik February 4, 2016, 6:14

            My guess is that KIC 8462852 has remained constant since 1989 or may have brightened slightly.
            I think that a “structural break” (at the Menzel gap) is a better interpretation of the data than a century long “secular trend” in dimming. However, if KIC 8462852 continues to dim at the rate described by Schaefer then I guess I am wrong.

            The other big question is:
            What will happen in 2017 – will there be another 15-20% dimming event?

            • Harry R Ray February 4, 2016, 10:55

              Here are ALL of the magnatudes from the Boyajian paper:W4-9.423, W3-10.591+/-0.123, W2-10.456+/-0.020, W1-10.425+/-0.023, K-10.490+/-0.020,H-10.561+/-0.019, J10.763+/-0.021, IC-11.061+/-0.08, RC-11.368+/-0.024, V-11.705+/-0.017, ,and B-12.202+/-0.008(I assume that B stands for Bloe and V stands for Violet. Correct me if I’m wrong. I have no idea of what the other bands represent). MY question is:ASSUMING that KIC8462852’s light is being permanently blocked at some level ALL OF THE TIME(as in my thought experiment)what does say about the SIZE of the “items” doing the blocking. Can anyone help me out, here?

  • Marshall Eubanks January 28, 2016, 22:44

    Nice rant.

  • Chris January 28, 2016, 23:31

    Fantastic rebuttal, Bradley!

  • Caleb Wachter January 29, 2016, 0:17

    I understand the science purist’s need to condemn what is seen as substandard scientific methodology, but at the same time this is one of the rare situations where human fascination is essentially limitless.

    The tone of Schaefer’s remarks are abrupt, condescending, and far from positive even regarding the obviously intriguing case of Tabby’s Star. Disregarding just how much the general public is interested in this star is a huge mistake which could cost science valuable airtime.

    I don’t think the general public views scientists as infallible, and I don’t think they *should* view scientists as infallible. I think when something interesting comes up (the Next Cure For Cancer, a new energy source, something in the world of particle physics, etc..) it’s in everyone’s best interests to promote the ideas in order to capture public imagination.

    Science fiction leads science fact, and that’s just an expression of the human capacity for fascination. Scientists should be less fascinated and more dispassionate, but they also need to understand that it’s in everyone’s best interests to get more attention to things like Tabby’s star. If a few shells get broken en route to making this particular omelette, I don’t think people will be upset. But they will get upset if the scientific community doesn’t let them share in potentially epic moments in history like this one.

    • Rob olling January 29, 2016, 9:47

      Well, unfortunately, a paper that is wrong can severely affect the chances of people who do it right in getting funding, in this case for DASCH. I know of several other examples. So the scientific process is all nice and well, but one bad coffee bean can ruin a enormous batch, and people’s livelihoods (in this grant dominated era), and while science subdiciplines.

  • Paul Carr January 29, 2016, 0:42

    Dr. Schaefer – thanks for the interview week before last. It;s had nearly 1000 downloads so far.

    My suggestion is that you flesh out your preprint with data on the other three o the five check stars. There seems to be some confusion – people reading Hippke think you only used 2.

    In the meantime, I will try to get someone from DASCH on the Wow! Signal to talk about the robustness of the photometric calibration.

    • David Sliski January 29, 2016, 9:33

      HI Paul and Brad,

      As someone who worked on DASCH for three years (2011-2014) and now work in exoplanets, I’ve been following this discussion quite closely. Fascinating to say the least. The person you want to speak with is Dr. Jonathan Grindlay, the PI. He will be able to give you the answers you are looking for.

      • Paul Carr January 29, 2016, 14:33

        Thanks, I have emailed Dr. Grindlay. I’m hoping to capture some audio from him or a member of the DASCH team.

  • Rafik January 29, 2016, 10:56

    Two major mistakes in Hippke’s paper have been identified here.
    – That Hippke used Red, Yellow and Blue sensitive photographs whereas only the Blue sensitive photographs should have been used, and
    – that Hippke included data with “known defects”.

    Due to these errors the whole of Hipke’s paper is then called into question, with some justification.
    Two issues raised by Hippke should be examined in depth to see whether there remains any support for his criticism of the findings by Schaefer.
    – That there exist small secular dimmings/brightenings in other F stars over the century 1890-1989 calling into question the uniqueness of KIC 8462852, and
    – that there is a “structural break” in the data for KIC 8462852 during the Menzel gap (accounting for the majority of dimming rather than an overall secular trend).

    The first issue seems to be adequately dealt with in the response by Schaefer.

    The second issue is not even mentioned by Schaefer in his response.

    I suggest that there remains some problems in Schaefer’s findings due to:
    – the use of 5 year bins rather than yearly bins (or raw data) as some data trends may be masked and unjustified “weighting” is given to data bins with few observations compared to data bins with hundreds of observations,
    – the reliance on early data (first decade or so) which is of poorer quality to (in part) justify a secular trend, and
    – the lack of recognition that the data is better fitted by two lines broken at the Menzel Gap (it appears that the majority of the dimming of KIC 8462852 occurred during the Menzel gap not during the other 85 or so years).

    I am not even a novice in this field – but I love data (whole career spent analysing data – yeah sad I know).

    • Waiting for 4MOST January 29, 2016, 13:24

      “Two major mistakes in Hippke’s paper have been identified here.”

      I feel like I’m going mad here but could someone please correct me if I am wrong, Hippke discusses the affect of Schaefer quality control cuts in the paper. He said they didn’t affect his conclusions:

      “We note that our results remain virtually identical if data cleansing, as described by Schaefer (2016), is applied.”

      Now I’m not taking that as gospel but it looks like the paper is being misrepresented. It seems to me that there is no mistake and this sentence has just been missed by the author of this article. A lot of criticism is being thrown around and it doesn’t really seem justified.

      I agree with your other points.

      • Rafik January 29, 2016, 23:05

        In reference to Hippke’s statement:
        “We note that our results remain virtually identical if data cleansing, as described by Schaefer (2016), is applied.”

        Hippke finds a slight brightening trend over the century (excluding the Menzel gap structural break). The Schaefer paper shows a dimming over the century (even if we exclude the Menzel gap) and take a ‘structural break” view of the data.
        My quick analysis of the data used by Schaefer also shows there is a slight dimming during those two periods – so obviously choice of data and technical analysis does have an effect.
        Both studies would benefit from a ‘sensitivity” analysis – clearly showing the effects of using:
        a – alternate datasets (blue versus red, yellow and blue, all data versus data cleansed a 1 mag variance and 0.5 mag variance),
        b – raw data versus annual and 5-year bins,
        c – an “overall secular trend” versus the “structural break” analysis, and
        d – using the 5 comparison stars (Schaefer) versus and wider dataset of F stars (I think we can exclude variable stars here).

        If both parties conducted such a “sensitivity” analysis I think we would find them coming a lot closer to a “joint” understanding of what the data is telling us about the long term magnitude variations of KIC 8462852.

        Another alternative would be for a third party to do this and claim credit for undertaking a thorough analysis of the Harvard plates for KIC 8462852.

  • Harry R Ray January 29, 2016, 10:58

    In defence of HIPPKE: I believe his methodology is more “cutting edge” than “sloppy”. This also leads him to sometimes take on issues that are somewhat out of his element. Cases in point: on his work on exomoons, he follows Rene Heller’s practice of “binning” data instead of the more respected process(promoted by the LEADING EXPERT on exomoons; David Kipping) of examining Each transit INDIVIDUALLY. As for his BROAD predictions on Fast Radio Bursts(and the mysterious 187.5 dispersion measure correlation), at least ONE FRB(the only one NOT detected by Parkes) has been PROVEN TO BE OF AN EXTRAGALACTIC NATURE, due to the fact that it is CLEARLY ASSOCIATED WITH A NEBULA! Cutting-edge methodology produces many WRONG results, but when it IS right, it ADVANCES science MUCH MORE QUICKLY than it would be otherwise possible to do so. Marshall Eubanks: “rants” are sometimes NECISSARY to clear the air on a controvercial subject. Case in point: When David Gray cane out with a refutation of Mayor and Queloz’s 51 Pegasi b’ discovery, the following day, they went on the internet with an EVEN MORE SCATHING rebuttal than Schaefer’s rebuttal of Hippke et al.

  • Svein Ove Aas January 29, 2016, 12:50

    Definitely the most interesting puzzle in a while. There’s one question I’ve been wanting to ask–

    Are there any visible changes in other stars that are physically close to Tabby’s? I assume not, or you’d have mentioned it, but I’d like to be sure.

  • Alex Tolley January 29, 2016, 12:51

    I would be a little wary of assuming that the DASCH team is teh last word on this. A similar controversy happened in 2012 when the ENCODE project published that 80% of the human genome was functional. The problem was how this was defined and caused a lot of controversy. Sometimes big teams don’t necessarily get it right, even if the smart money would bet on them.

    Given this interesting result of dimming, it would make sense to see how unusual this is first. If Tabby’s star is fairly unique, then it requires an explanation. Given the apparently rapid dimming, shouldn’t this be measurable with another decade of observations to confirm it with purely electronic instruments?

  • Michael January 29, 2016, 13:28

    I have checked all the stars in Table 1 of

    http://arxiv.org/pdf/1601.07314v1.pdf

    almost all lie in gas poor regions, the antagonist KIC 8462852 is a gas rich area.

    http://aladin.u-strasbg.fr/AladinLite/?target=KIC%208462852&fov=37.03&survey=P%2FDSS2%2Fred

    Could these clouds be responsible for the ‘century’ dimming effect with the rest as ‘error’ in the magnitudes on the plates. To be honest looking at some of the plates they are in a poor state?

  • DJ Kaplan January 29, 2016, 13:31

    Will we ever know for sure?

    • Michael January 29, 2016, 15:12

      If we stop trying to know for sure are we not equally guilty of trying to not know for sure?

  • Ashley Baldwin January 29, 2016, 13:56

    The world has changed . And speeded up. “Debate” that would previously have taken weeks in “letters to the editor ” is now played out in blogs with informal peer review at near real time .

  • Sean Robert Meaney January 29, 2016, 21:10

    Failures in data: If the image quality decays over time and result in dimming then to reach the ‘twenty percent dimming over a century’ line, later photographs would be decaying at a quicker rate than older images.
    The error curve would be a logarithmic curve where in the oldest images had failed the greatest and the newest images the least so their accuracy would be higher.
    Technological changes in photoplate imagery mean that there are different logarithmic curves of failure in image quality for each change in technology. It means the newer the data, the least the error variation and rate of variation in the data. Unless a newer method of photograph made things worse.

  • Erik Landahl January 29, 2016, 21:20

    Schaefer is right to be pissed. Funding is based on perception, and Hippke’s broadside could really screw over how the money folks perceive DASCH.

    The principle of parsimony points toward ETI. Occam’s Razor is steadily shaving away natural causes and human error. But the scientific community seems to hold an unspoken quasi-religious belief that human intelligence reigns alone in the universe.

    The idea that the KIC 8462852 data might be caused by 648,000 2oo-km wide comets in a highly elliptical orbit was embraced by the scientific community. That theory was way out there but mainstream science was ready to trumpet it as gospel the next day – because ETI was sidestepped and that’s what really matters. Whew.

    The insane comet cloud was ruled out. Unwittingly perhaps, Hippke is the latest hope for mainstreamers to discredit ETI. Cast seeds of doubt about the data. See what germinates.

    The ETI megastructure theory neatly fits the data – if a “natural” cause fit the data as perfectly, the scientific community would warmly accept it. But a pre-Copernican mindset quietly permeates their worldview, and nothing threatens it more than ETI.

    Attributing the KIC 8462852 data to error will be proven right or wrong. Natural causes have failed to date. If error isn’t found, if natural causes are finally ruled out and the data stands up, will ETI be accepted? Or will the next “reasonable” explanation come along? Maybe a ring system of primordial dark matter black holes? Anything but ETI.

    Grab a Norman Camembert, a Columbia Valley Merlot, stay tuned to Centauri Dreams, and enjoy the show.

    • Realpra1 January 30, 2016, 1:54

      Well put, my feelings exactly. I feel there’s put undue weight to other natural causes a bit too quickly.

      However I don’t think they can brush this one under the rug – if its a Dyson swarm growing exponentially then the entire star will disappear mostly or completely from view in our lifetime, maybe as soon as 2030.

      My popcorn is ready for them trying to explain entire stars disappearing for “totally normal reasons” though.

    • Eniac January 30, 2016, 15:03

      “might be caused by 648,000 2oo-km wide comets” I think it is 600 10 km comets (http://arxiv.org/pdf/1511.08821v1.pdf), and it was not ruled out by any means.

      • Realpra1 January 31, 2016, 11:25

        Can’t comment on the details, but that was before Schaefers results.

      • Erik Landahl February 1, 2016, 10:44

        If I got the number of comets wrong I apologize. I’ll find the article I read; if it did say 648,000 I’ll post the link.

        The size per comet however was 200 km or larger. 10 km comets would be too small. I’ll check that number and post the link.

        Re: comets ruled out, I’ll find that article and link as well.

        • Paul Gilster February 1, 2016, 15:29

          Erik, you’re talking about Schaefer’s number here, right? The 648,000 comets are originally found in his dimming paper:

          http://arxiv.org/abs/1601.03256

          • Erik Landahl February 2, 2016, 10:50

            Thanks much Paul, I appreciate it!

          • Eniac February 5, 2016, 1:32

            The 648,000 number occurs only in the abstract and appears pulled out of thin air. Does anyone know how it is derived?

        • Eniac February 5, 2016, 1:28

          Bodman and Quillan give two scenarios that result in sufficient dimming in their model: One involves 73 comets of R~100 km, the other 731 comets of R~10km. I was referring to the second.

    • Harry R Ray February 2, 2016, 10:42

      Right and wrong. Most astronomers DID embrace the “comet cloud” theory, BUT, with a grain of salt. CASE IN POINT: Bodman and Quillan strongly supported it,but with ONE MAJOR EXCEPTION: The “Q8” lightcurve, which they AVOIDED as if it were the plague! The reason they gave for this is that it was too SYMETRIC! But, in reality, it isn’t. INGRESS is more than two times as long as egress(in an earlier coment, I thought the ratio was LARGER than 3 to one, but since then, I did some “science” on my own, turning the lightcurve int two triangles, and found that ratio is MOST LIKELY either 2.3 to 1 or 2.4 to 1. However, I chose ingress START and egress END points based on naked eye observations of the lightcurves. Someone should STILL look at this with a MICROSCOPE TO MAKE SURE that the ratio inn’t LARGER, like 2.718, or e)! Maybe they saw this,too, and just AVOIDED it so that the microscope work would NOT reveal a possible MESSAGE!

  • Jens Wilkinson January 30, 2016, 0:44

    I think the last comment has it all wrong. I would love for this to be ETI. I know that many scientists agree. But because I would find it exciting, I fear that I might be biased and so I want to look at other possible explanations to ensure that I’m not jumping to a conclusion only to be ultimately disappointed.

    • Realpra1 January 30, 2016, 13:18

      At this point making a life hypothesis and trying to test it makes perfect sense wheres disproving every possible imaginable thing would take forever.
      As it stands a simple life hypothesis assuming efficient, but boringly normal solar collectors and normal exponential growth (~1-3%/yr) fits all seen data – not just the light curves.

      This gives you real ideas to check for such as:
      1. Continued growth beyond 1989, possibly fitting an exponential curve.
      2. Given better (long exposure?) radio telescopes, potentially increased weak white radio noise in the area averaged over all frequencies.
      3. Potentially interesting absorbtion curves due to chemical makeup of collectors.
      4. The cloud causing gradual dimming and objects causing the transit curves being of the same material – in other words we are in fact watching a constant transit event that we could check right now.
      5. ?

      Hopefully the scientific community is just being slow though and not religious.

      • Rob Henry January 30, 2016, 21:23

        ETI solar collectors does not fit the data given the lack of IR, but ETI solar reflectors could. If that Dyson swarm was mass limited, solar sails might be being used to keep its sectors in place, and these sails may well make us 99% of its area, even if only 1% its mass. The main mass of these sectors could be doing anything, but it would be reasonable to suppose that they are solar collectors. Is this what you meant?

        • Realpra1 January 31, 2016, 11:15

          Before anything else:
          The missing IR means nothing, we can’t detect less than 100K temperatures and background temperature is only 2.7.
          So if they are efficient they would have a ton of room to radiate in that we wouldn’t see.

          Even the night side of Mercury is only 100K so I don’t see why everyone expects efficient alien solar panels to waste more energy than a rock.

          I meant that the dimming and the transit events are caused by the same material only in different concentrations.
          At least that would make sense if it is ETI because the concentration of space constructions would be greatest around their planet(s).

          Imagine mankind in 10.000 years or more:
          You would have two great clouds of space construction around Mars and Earth and then a diffuse cloud all around the sun – which would look just like Tabby’s star’s light curves/dimming seen from afar.

          IF their planets are still there in some recognizable form the transit could show us oxygen, water or industrial gas absorption traces I suppose, but the majority should have identical absorption lines as right now.

          • EricSECT February 2, 2016, 6:37

            Realpra1: “The missing IR means nothing, we can’t detect less than 100K temperatures and background temperature is only 2.7.” Does this mean that it is impossible to detect <100K IR "ever", or just with our current technology? If just technology limitations, what would we need to do to make this happen (ie: A dedicated satellite?)? IF there is IR being emitted, it's either that it's (1) emitted in a window we are not monitoring OR (2) directed away from us (and either case could have work being extracted first). Can anyone think of a natural processes that can do (1) or (2)? ….or both at the same time?

            • Realpra1 February 3, 2016, 15:38

              Just the current technology.

              Spitzer actually has a detector for 160 um which should theoretically correspond to a 17K black body temperature.
              I’m not sure if that is correct or if it was used though.

              However there is probably also a certain threshold for the amount of radiation below which we cannot detect it. That limit may also vary with wavelength/temperature.

              I got the 100K limit from a galactic survey looking for Dyson spheres and as the night side temperature of Mercury.

  • Paul Carr January 30, 2016, 1:57

    There os a fairly solid plan that I will interview Harvard’s Professor Grindlay (PI od DASCH) next week. Apparently, he agrees with Schaefer that Hippke is all wet, but I want to know in detail why this is so. Any questions for him?

    • Rafik January 30, 2016, 9:55

      The raw data, Schaefer’s 5-year bins version, Hippke’s analysis (including red and yellow) all show that there is a clear break in the data at the Menzel gap for KIC 8462852.
      I would argue, that two distinct lines of best fit with a “structural break” (pre 1952 and post 1967) rather than a single line “secular trend” over the century provide a better explanation of the change in magnitude for KIC 8462852.
      I would like to know if Schaefer has considered a structural break at the Menzel gap as a better explanation than a secular trend.
      Has Schaefer looked at the effect on his results by examining the raw data (blue sensitive only) or annual bins compared to his 5-year bin technique?

      • Paul Carr February 1, 2016, 10:55

        You’re going to have to write that up before it becomes a question I can ask Prof. Grindlay. I haven’t seen your argument in detail.

        • Rafik February 1, 2016, 21:28

          Rather than going into arguments about different datasets and processing techniques, I think it better to raise questions as points of clarification.
          These questions relate solely to Dr Schaefer’s analysis of the Harvard plates.

          The three questions are.
          1. What confidence should we have regarding the early Harvard plates as there appears wide fluctuations in magnitude up to 1910 in all three stars in Dr Schaefer’s paper?
          2. Has Dr Schaefer investigated the effect of using annual bins or raw data in comparison to his 5-year bin technique?
          3. Has Dr Schaefer considered that a distinct structural break in the data at the Menzel gap, with a much smaller secular dimming trend in the pre and post Menzel gap periods, provides a better explanation of the Harvard data than an overall secular dimming trend over the century?

    • randomengineer January 30, 2016, 16:23

      q: Is the 100 yr dimming done as statistical e.g. linear regression only or is there evidence of ‘surges’ or otherwise highly active periods and/or plateaus? Periods of more and less dimming? If so does this suggest known or new natural processes?

    • Larry January 30, 2016, 18:13

      KIC 8462852 and the 5 check stars are on the earliest plates. They should also be in the Kepler data. Assuming the check stars are constant in brightness, the plates and the Kepler data can be calibrated. Then KIC 8462852 can then be compared against the check stars in 1890 and in 2013 to determine the size of any magnitude change. If there is nothing strange going on with KIC 8462852, the change should be zero +/- some uncertainty. You guys can argue about gradual, continuous change vs. step-like drops, binning, the Menzel gap, etc. I’m just curious about that one gross measurement of 1890 compared to now: Did it dim, and by how much?

      • Rafik January 31, 2016, 3:29

        If we use a straight linear projection of the trends in the Schaefer paper for KIC 8462852 and TYC 3162-879-1 we should see KIC 8462852 around 0.025 magnitude dimmer than TYC 3162-879-1 by around 2012 (rough estimates of 12.488 to 12.463).
        Kepler mag measurements show that KIC 8462852 is brighter than TYC 3162-879-1 by 0.01 mag (12.08 compared to 12.09).

        There could be heaps of reasons for the differences as we may not be comparing the same optical bands (Harvard is blue – Kepler not sure) and the magnitude measurements for TYC 3162-879-1 seem to jump around a fair bit in the Harvard plates.

        Short answer is that it is not obvious that KIC 8462852 is continuing to dim at the same rate as described by Schaefer based solely on Kepler magnitudes. We really need to find comparable data that overlaps between the Harvard plates and Kepler to ascertain if dimming has continued, accelerated, halted or reversed.

  • Eniac January 30, 2016, 15:09

    Schaefer:

    This dimming from the DASCH data is just a long-time scale version of the dimming also seen with the Kepler spacecraft

    Is anyone else thinking that this seems like a conclusion being jumped to without a shred of evidence?

    The only link between the two is the claim that they are both unique, and thus must have the same cause. Really?

    Besides, as we are seeing the jury is still out on how unique the apparent dimming is, you need hundreds of comparison stars to show that, not 2 or 5.

    • Rob Henry January 30, 2016, 20:47

      ENIAC, this is the second time you brought this up, but this time you dropped the context. As you acknowledged prior, Schaefer’s assumption makes perfect sense on the grounds of parsimony, if the measured dimming is unprecedented, or a one in a million event. The question then is why don’t astronomers sit twiddling their thumbs for year until that premise is tested, and only then begin to speculate on the potential for an ETI explanation.

      Part of the reason is that premise is already part of their default assumptions, especially regard theory for F behaviour. Another is the nature of science itself, where the greatest advancements come from results the can’t be fitted into the current paradigms – such that it becomes wasteful not to anticipate those events. Finally, this is the forum for astronomical speculation that hold rigorously to scientific principles. You could almost say, that if this opportunity was not taken, it would be evidence that science was beginning to transform from the beloved discipline we have known since the time of Newton.

      • Eniac February 5, 2016, 1:09

        Rob, I find your suggestion that astronomers have nothing better to do than either speculate on ETI explanations or twiddle their thumbs offensive :-)

        Seriously, what matters is not the frequency of the hypothesized explanation (actual dimming of a star), but the frequency of observing similarly suggestive data for other stars, using the same method. In other words, what matters is the frequency of positives, both true or false. Given this, Hippke did exactly the right thing. Whether he did it right or expertly enough will require an expert to judge, preferably someone less involved than Schaefer.

        • Rob Henry February 5, 2016, 16:37

          Sorry. I only meant to imply sitting on an idea, by that phrase.

  • Larry January 30, 2016, 17:15

    Is it your argument that the long term dimming of Tabby’s is the same phenomenon found by Kepler. Are you suggesting that whatever is blocking the light of KIC8642852 was picked up by observations over that last 100 years. Given that Kepler detected irregular periodic dimming it must be extraordinarily lucky that the archived photos happened to capture the same. Can you explain.

    • Local Fluff January 31, 2016, 8:48

      The anomal dips in Kepler data only occur (as far as it looks to me) when the space telescope is oriented in the same way, thus pointing the same part of the CCD towards that star. Has this really been looked into? Has it been ruled out that the anomalies were somehow caused by some slight defect in the telescope itself? The dips don’t seem to have the shape expected from transits.

  • Michael January 31, 2016, 8:00

    Tabby’s star is showing clear signs blurriness and dimming

    http://aladin.u-strasbg.fr/AladinLite/?target=KIC%208462852&fov=0.07&survey=P%2FallWISE%2Fcolor

    Compared to two F type control stars

    KIC 12253106

    http://aladin.u-strasbg.fr/AladinLite/?target=KIC%2012253106&fov=0.07&survey=P%2FallWISE%2Fcolor

    And KIC 8323104

    http://aladin.u-strasbg.fr/AladinLite/?target=KIC%208323104&fov=0.07&survey=P%2FallWISE%2Fcolor

    There is clearly material along the light of sight to Tabby’s star and this material may be changeable in optical density over short time spans. In my mind dimming is occurring but the deep dips point to something else more locally.

    • Paul Carr February 1, 2016, 11:01

      I don’t see it. Do you mean just in the allWISE data? If there was some interesting infrared scattering going on, it’s not clear to me you would see it as “blurry”. In the DSS data it looks perfectly normal, and there were no unusual spectral lines reported. We’re going to need something quantitative I believe.

    • FrankH February 1, 2016, 16:38

      I don’t see it either. Other than instrument artifacts, all three stars look the same, even in the 2MASS images.
      KIC 8462852 does seem to have a small extension to the south-south-west that appears in the 2MASS and DSS2/blue images, but that could just as easily be an artifact/diffranction spike.

  • kzb February 1, 2016, 8:23

    Michael, I’m afraid I don’t perceive the blurriness compared to other stars in those images. Is there some objective measure of “blurriness” ?
    If so this is very important, because that would enable us to differentiate between intrinsic stellar variation and material along the line of sight.

  • Alex Tolley February 1, 2016, 21:08

    Naive question. How are star intensities measured from photographic plates? Is it in any way like measuring small areas on any film – surround the area and sum the pixel values? My experience in another domain – measuring intensities of radioactive phosphorus of labelled RNA for transcription levels showed me that this isn’t a straightforward problem. Is there any similarity for measuring stars?

    • Paul Carr February 1, 2016, 23:10

      There are no pixels on photographic plates. It takes some expertise, but it is primarily a comparison of the size of the image to known calibrated stars on the same plate.

      • Alex Tolley February 2, 2016, 14:16

        I realize that photographic film has no pixels, but don’t the plates have to be digitized first to perform analyses?

  • Paul Carr February 1, 2016, 23:06

    I won’t asked Dr. Grindlay to answer for Schaefer. The early plates are interesting. I asked Schaefer about the 1900s dips. He wasn’t sure they were rea, and not statistical flukesl. It’s easy to be fooled by randomness.

    http://www.wowsignalpodcast.com/2016/01/season-3-episode-3-slow-and-fast.html

    • Rafik February 2, 2016, 10:59

      Ok – thanks.

      So the 1890s and 1900-1910 data may have a bit of uncertainty to them.
      Maybe we should be commencing the data analysis at 1910-15 to remove that uncertainty.

      Could it be possible that the dimming of KIC 8462852 is a super version of Epsilon Aurigae ? The eclipsing component would have to be a cool brown dwarf with enormous dust disk to explain the lack of IR.

      Sounds more realistic than 600,000 giant comets.

      • Harry R Ray February 3, 2016, 10:24

        A “Millenium Transit”. I thought about this one for a while right after the Schaeffer preprint came out. I rejected it because either the disk around the BD would have to be SO HUGE that it would DWARF the Beta Pictoris disk, or the alighment would have to be SO PERFECT that the BD would act as a LENSE STAR, and KIC8462852 would actually be BRIGHTENING due to the microlensing MORE than it would be FADING due to the TRANSIT.

  • Sascha Wageringel February 2, 2016, 7:04

    As far as the impact on public opinion is concerned, generation Google relies heavily on Wikipedia for reference, make sure the entry for KIC 8462852 clearly reflects the validity of the dimming, linking the respective papers. Its no witchcraft if you can file a valid reason for the entry. Just post under the discussion tab the changes you like to propose, why you deem these necessary and link your reference and you should be good to go.

  • kzb February 2, 2016, 8:30

    Michael: That last image is interesting (the Mellinger one) because it shows the whole area seems to have some nebulosity. If that is in the foreground, you would expect comparison stars at similar distances to show a similar effect (which apparently they don’t).
    Alex Tolley: maybe you are on to something here ! The point being, depending on how the total luminosity is measured, apparent dimming may be detected simply because the light is spread over a larger area of the plate compared to the comparison stars. Not because the intrinsic luminosity has changed.
    On the other hand, these historic images have been taken through the atmosphere. The photographic images of all stars are much larger in area than their true angular sizes. In fact, would this observational blurriness not completely overwhelm any blurriness at source? It might be possible to detect blurriness at source by careful image analysis, comparing the image in question to others on the same plate. But if the observational noise is orders of mag higher it is going to be a struggle.

  • Paul Carr February 2, 2016, 12:03

    Anyone familiar with the Galex catalog? I was fooling around in Aladin:
    https://drive.google.com/open?id=0B_LvagsQCx-caFBTemJnb0FqXzg

    and I noticed that Galex has two NUV sources cataloged right on top of Tabby’s star of about the same magnitude, and in very slightly different positions:
    3728666168841474091
    6371584312244963880

    Here’s a picture:
    https://drive.google.com/open?id=0B_LvagsQCx-cV1c5amdyUVlBY2M

    It’s probably nothing – just two entries for the same star, but I’m not up to speed on Galex and wonder how likely this is.

  • FrankH February 2, 2016, 16:26

    “Planet Hunters X. KIC 8462852 – Where’s the flux?”
    T. S. Boyajian et al.
    http://arxiv.org/pdf/1509.03622v2.pdf

    This paper has Keck AO images of KIC 8462852, its companion(?) as well as spectra showing interstellar absorption features in the line of sight. Good discussion as well. Worth reading, since it addresses some of the questions in this thread.

    • JonG February 3, 2016, 7:32

      The AO image in Figure 7 from the Boyajian paper shows a lot of structure/lumpiness around KIC 8462852. Is that likely to be real and expected, or an artefact of AO processing?

    • Michael February 3, 2016, 9:41

      Looking through the article again there is mention of Sodium D although it is put down to stellar and interstellar clouds in the line of sight. So there is gas present but no indication is given of how much.

      page 6

      ‘While interstellar medium features are not typically related
      to indicators of astrophysically interesting happenings in stars, we
      note the presence of stellar and interstellar Na D lines in our spectra.
      In the bottom panel of Figure 5, we show a close up of the
      region containing the Na D lines (5890; 5896A° ).Within the two
      broad stellar features, there are two very deep and narrow Na D
      lines with split line profiles, indicating the presence of two discrete
      ISM clouds with different velocities of 20 km s􀀀1.’

      Sodium is also detected in this planets evaporating atmosphere.
      http://www.nasa.gov/vision/universe/newworlds/Osiris_leaks.html

    • Michael February 3, 2016, 16:40

      This is a spectrum shot of WASP 17b (1000 lyr, F6V), remarkably similar are the sodium D lines of Tabby’s (1400lyr, F3) star indicating interstellar clouds in the line of sight but in much greater depth.

      However they indicate that two of the deep lines are from the star and the side ones on each are from an interstellar dust cloud which contradicts was I understanding from the paper (they state two clouds?). From what see there is only one cloud (right spike) and it is quite deep. Is it an evaporating planet cloud with sodium or an interstellar cloud containing sodium? Both sodium dips are quite deep, much deeper than HD 209458b which is an evaporating planet.

      http://www.exoclimes.com/topics/the-hot-jupiter-hd-209458-b/

      http://inspirehep.net/record/878233/plots

      http://arxiv.org/pdf/1011.4385.pdf

      Much to learn about this weird star!

      • Michael February 3, 2016, 22:55

        There is an awful lot of sodium in the spectrum versa normal F-types,

        http://www.handprint.com/ASTRO/IMG/specprf.gif

        My take is the first of the sodium D dips is a planet/moon and star contribution and the second dips on each sodium line indicates interstellar material possibly even from the long term evaporation events (long term dimming maybe?). They say it is two interstellar clouds, maybe not.

  • ljk February 3, 2016, 11:36

    If it’s not a Dyson Swarm and it’s not a flock of comets, then what is it?

    http://www.space.com/31810-alien-megastructure-star-flickering-mystery-continues.html

    • Paul Carr February 3, 2016, 14:09

      Truthfully, no one knows. It could be a very cold Dyson swarm (some of the millimeter wave data posted earlier hints at this, but is inconclusive), but frankly, a Dyson swarm is a pretty simple model of harvesting a star’s energy – scaled way up from the way humans have been doing it since the middle of the 20th Century, and it’s not clear at all what the energy would be used for or how it would be distributed. I think we should consider the Dyson swarm as more of a toy model or a mental lens rather than scientific hypothesis.

      The search is far from over for some exotic – or at least very rare – astrophysics that could explain the dimming, even as work proceeds to measure it better. I’m optimistic about this latter – we have a history of wrapping our heads around some pretty exotic stuff in a generation or two, even when it’s discovered completely by accident, such as gamma ray bursts.

      I just wish the MSM would stop jumping on every conjecture that gets thrown out before them, no matter how much of a stretch it is.

      • Michael February 3, 2016, 15:35

        ‘I just wish the MSM would stop jumping on every conjecture that gets thrown out before them, no matter how much of a stretch it is.’

        That may be so but the artwork that has come from this is amazing!

        https://media.licdn.com/mpr/mpr/AAEAAQAAAAAAAAZJAAAAJDY2MzBkOTE0LTM2ZDQtNDVhYS05MzViLWYwNmQ1NGUzZTY2ZA.png

      • Harry R Ray February 4, 2016, 11:12

        Paul Carr: Speciffically WHICH “millimeter wave data posted erlier” are you talking about(i.e frequency RANGE and observed by WHICH facility:Spitzer,IRAS-Spx, Allen Array, or OTHER)? RSVP!

        • Paul Carr February 4, 2016, 17:04

          None of those are mm wave facilities. This was done on Mauna Kea using the Sub Millimeter Array and the SCUBA-2 camera:

          http://arxiv.org/abs/1512.03693v1

          It’s an interesting paper, and almost none of it was written with the caps lock key down.

      • ljk February 4, 2016, 18:07

        Paul Carr said on February 3, 2016 at 14:09:

        “Truthfully, no one knows. It could be a very cold Dyson swarm (some of the millimeter wave data posted earlier hints at this, but is inconclusive), but frankly, a Dyson swarm is a pretty simple model of harvesting a star’s energy – scaled way up from the way humans have been doing it since the middle of the 20th Century, and it’s not clear at all what the energy would be used for or how it would be distributed.”

        I would like to think it is powering an alien supermind (aka Matroishka Brain), but it could just as equally if not moreso be for a megaweapon:

        http://www.orionsarm.com/eg-article/48fe49fe47202

        • Paul Carr February 4, 2016, 22:44

          OK, so what then are the observables? I haven’t seen any calculations.

          • ljk February 5, 2016, 12:45

            So would I.

    • Harry R Ray February 4, 2016, 10:31

      Some of MY leading candidates are as follows. NATURAL:Almost certainly now, some INTERNAL PROCESS that we haven’t even CONCIEVED OF yet. This is, however, based on the ASSUMPTION that KIC8462852 is a SLIGHTLY evolved star(i.e. subgiant) star. That’s right! If KIC8462852 is PROVEN BEYOND A SHADOW OF A DOUBT to be a main sequence star, I will be FIRMLY IN THE “NON-NATURAL CAUSE” camp! NON-NATURAL: Shkadov Thruster, Matrioshka Brain, “Black Monoliths”(If Arthur C. Clarke were alive today, I wonder what HIS take on this would be?”

  • Paul Carr February 4, 2016, 10:10

    Hopefully, the intrepid observers at the AAVSO will be watching if it does, since Kepler has not been on Tabby’s Star since 2013 when the reaction wheel failures took it out of its primary mission.

    If they do catch it in the act, it will be important to get good spectra in all bands during the event. A few years later, and who knows – we might even get JWST on it.

  • Alex Tolley February 4, 2016, 18:12

    @Harry Ray – if you want to make text stand out to highlight a point, you can use the italic or bold (or both) html tags. All caps makes it seem like you are shouting.

  • Paul Carr February 5, 2016, 12:15

    It’s on page 8. He doesn’t show his arithmetic, it is true.

  • ljk February 5, 2016, 16:52

    Berkeley SETI Chief says Tabby’s Star is probably not surrounded by any Dyson Swarms:

    http://alumni.berkeley.edu/california-magazine/just-in/2016-02-05/wtf-star-some-suggest-its-evidence-aliens-berkeley-seti-chief

    Unless one is found, then he will say he knew it all the time! :^)

    • EricSECT February 5, 2016, 19:44

      I find Andrew Siemion’s “argument” against ETI as an explanation for Tabby’s Star anomalies totally unconvincing. I would have expected more of an open mind from SETI. Nothing will get decided until we have more data to crunch: Watch this star for 5 more years with every scope we can summons, including real time with the HST, and another satellite scope to look for excess IR at a window we currently can NOT monitor (<100K?). Look for long term dimming over the 5 years and transits if they again take place. Is that red dwarf a true companion star ….or it just passing by and has it gravitationally perturbed Tabby's…. or is it simply in the foreground? Nail it down. And Harry R. Ray? I am a FAN of your CAP LOCK typing, please DON'T ever change.

    • Realpra1 February 7, 2016, 19:06

      Tabby’s star has little to no rotation so its pretty sad he brought that up as a potential natural cause.

      Why is he head of SETI?

      • Paul Carr February 7, 2016, 22:29

        He’s not head of SETI, since there is no such organization. He’s just science head of Berkeley’s SETI effort. He’s a bright, articulate young guy (I’ve interviewed him twice).

        Tabby’s star is a fairly rapid rotator with a period of 0.88 days. Compare that to 25 days for our sun.

        • Realpra1 February 8, 2016, 11:10

          But is “fairly rapid” rapid enough to create a severely oblate star required to produce the weird light curves?
          Can it also explain the dimming?

          The article I read about the theory concluded that the rotation was insufficient.

          I’ll leave it to experts for now.

  • Paul Carr February 6, 2016, 18:34

    Here’s my interview with Josh Grindlay of DASCH:

    http://www.wowsignalpodcast.com/2016/02/burst-11-dasch-photometry-with-dr-josh.html

    He is sharply critical of Hippke, but also skeptical of Schaefer’s result.

    • Paul Gilster February 6, 2016, 22:11

      Needless to say, Paul, I’m extremely interesting in hearing this. Thanks for the link!

    • Rafik February 6, 2016, 23:30

      Great interview Paul.

      Dr Grindlay has provided a great overview of the DASCH photometry data and good summary of the problems that can happen in interpreting datasets:
      – the effects of including outlier/flagged data that is questionable,
      – the effects of binning data especially if using broader bins such as 5-years), and
      – the effects of comparing brighter stars (near saturation points for the photographic plates) with dimmer stars such as KIC 8462852.

      I have serious concerns about the validity of including data from the first decade or so in any long term analysis of KIC 8462852. Dr Grindlay seems to share concerns about the early data in this interview.
      If there is any long term dimming trend it should be recognisable in shorter time spans (eg 1910-1950 and 1970-1990) which to me look very flat.

      I look forward to Dr Grindlay’s paper on this topic but it appears that he thinks we are looking at a star with basically a flat magnitude over the 100 years of the DASCH records.
      I would be very interested to know if Dr Grindlay considers the “break” in magnitude that appears during the Menzel gap to be real or an artefact of the change in Telescopes/emulsions. Obviously a comparison of the Landolt photometric standard stars (and possibly a range of nearby stable F stars) before and after the Menzel gap would settle this question.

      A very simple look at the data for KIC 8462852 at the Menzel gap shows the following:

      Period Observations Ave Mag
      1915-17 67 12.340
      1950-52 80 12.362
      1973-77 66 12.450
      1986-89 83 12.458

      This shows that in 35 years to the early 1950s KIC 8462852 dimmed by .022.
      In 24 years to the mid 1970s KIC 8462852 dimmed by .088.
      In 13 year to the late 1980s KIC 8462852 dimmed by .008.

      Annual dimming rates for these periods are .0006, .0037 and .0006 respectively. I would consider these dimming rates negligible apart from the Menzel gap.

    • Michael February 6, 2016, 23:45

      Thanks Paul, great to hear some of the argument about the subject. Although it does appear that Hippke has made some bad choices of target stars and binning techniques leading to bad statistics Dr Josh Grindlay also takes issue with the Schaefer paper.

      So this one is still up in the air so to speak and we will have to wait for some more papers before it is cleared up.

      • Rafik February 7, 2016, 10:07

        I think Dr Grindley was taking aim at Dr Schaefer when he discussed binning techniques.
        Dr Schaefer used 5-year bins that could vary significantly depending on which year you start your 5-year period.

        If memory serves correctly Hippke used raw data without binning (and he included data points which were flagged as having quality issues).

        • Michael February 8, 2016, 15:42

          I went through it again and you are right, thanks for clearing that up. I was always suspicious of the older plates as I downloaded some and they looked iffy to me but there was the chance that it could have worked. We must note though that there are clouds in between us and the star as the deep sodium D lines indicates to us and that could cause dimming but how much I know not.

          Looks like they are back to the drawing board again.

    • Paul Gilster February 8, 2016, 9:06

      Paul, could you drop me a note at pag1877@gmail.com? I have a backchannel question for you.

  • Alex Tolley February 7, 2016, 13:10

    Very interesting interview with Dr. Grindlay. My sense is that he was saying in the most gentle way possible, that Schaefer’s analysis was sloppy and would need more work to pass peer review before publication.

  • Rob Henry February 8, 2016, 5:49

    @Alex Tolley, my sense is that Grindlay was saying in the most gentle way possible, that most old plates are flagged. What other way is there to explain such an extreme difference of opinion?

  • ljk February 9, 2016, 15:56

    How about a megamirror for pushing light sails across the galaxy:

    http://nextbigfuture.com/2016/02/physics-phd-reader-of-nextbigfuture.html

    If what is going on at Tabby’s Star is artificial, I get the feeling humans just are not advanced enough to quite get what may be going on there and why, though at least Dyson Swarms and megamirrors are a step in the right direction towards thinking outside our boxes.

    Maybe an AI could come up with something more interesting and closer to the truth? And yes I am referring to a contemporary AI.

  • Duffy February 9, 2016, 20:23

    http://www.cloudynights.com/topic/526551-patterns-in-the-dimming-of-kic-8462852/
    What do you think about this ? Probably just a coincidence.

    • Harry R Ray February 10, 2016, 10:36

      I agree. it probably IS just a co-incidence, and the kind of one the “Ancient Aliens” crowd just LOVE to harp on(I can’t Wait for the next season to see how they TWIST this ENTIRE story), but, if it ALSO turns out that the ingress-egress ratio of the “Q8” lightcurve is ALSO an “interesting” number(like e), all bets are off! A bit of breaking news: Hippke now claims a 1.5% “jitter”(from his tweet to Jason Wright) for KIC6366512 and KIC9909362 “no matter how it is cleaned”. As a result, I recommend that Schaefer ought to EYEBALL all of the plated for these two stars to look for a dimming trend similar to KIC8462852’s, and that these two stars should ALSO have their GAIA data extracted ASAP. It is possible that ALL THREE OF THESE STARS are part of a new stellar classification of slightly evolved stars with weird internal properties, and that KIC 6366512 and KIC9909362 just did not HAPPEN to display the SHORT-TERM FLUCTUATIONS KIC8462852 did during the four-year Kepler observation period.

  • Tom Mazanec February 10, 2016, 13:31
    • Harry R Ray February 11, 2016, 10:57

      YES! But, for what purpose? The only two that come to mind is a Schkadov Thruster in the process of EITHER CONSTRUCTION OR DISINTEGRATION, OR the mother of all lightsail propellers!

  • variable February 10, 2016, 14:33

    Looks like Hippke has significantly revised his paper: http://arxiv.org/pdf/1601.07314v2.pdf

    • Rafik February 12, 2016, 6:44

      Reading the revised Hippke paper reminds me of a classic movie from 1966. I think Hippke has again jumped the gun and needs to significantly revise this updated paper if it is to survive peer review.

      The Good
      1. Hippke has gone back and investigated the datasets available from DASCH and revised his paper thoroughly. He seems to have taken on board a number of criticisms made of his initial paper which is a credit to him.
      2. Hippke has attempted to provide an updated analysis of the KIC 8462852 light curve over the century 1889-1989 with more robust data eliminating datapoints that were “flagged” by the DASCH team. He shows that the best interpretation of the data is not a century long fade but a basically constant light curve with a structural break in the series at the Menzel Gap.
      3. Hippke has provided an analysis of “comparison stars” that are seen to be stable and “close” to KIC 8462852. This is a significant improvement on his earlier selection of 28 stars that included variables and stars “far” from KIC 8462852.
      4. Hippke has mentioned that the effect of a gradual dimming should be evidenced in a shorter selection of years and that it takes a selection of 1889 right through to 1976 or 1978 before a dimming trend becomes evident. Clearly a structural break at the Menzel gap is a better interpretation of the long term dimming for KIC 8462852.

      The Bad
      1. Hippke has not replicated Dr Schaefer’s analysis – it is unclear if he asked for the method of selection so he could replicate the data. He seems to have gone on a bit of a “fishing expedition” in his attempt to get the same dataset as Dr Schaefer.
      2. Although he provides a brief statement on the effect 5-year binning has on the results he does not mention the effects of varying the start of each 5-year period or the effect if annual binning of data was performed.
      3. He seems to ignore the fact that the early DASCH data (first decade) has quality problems as mentioned by Dr Grindlay and should be very cautious in including that data in his analysis.

      The Ugly
      1. I think Hippke has misinterpreted some of Dr Schaefer’s work especially the issue of “cleaning” data resulting in truncation of values above 12.45. I find no evidence that Dr Schaefer ignored data dimmer than 12.45, rather his data shows bins for 1982.5 and 1987.5 with magnitudes above 12.45. I do not believe Hippke’s comments in section 3.4 are helpful.
      2. Hippke has found a significant structural break at the Menzel Gap in the light curve for KIC 8462852. He then compares other nearby F stars and finds two with significant structural breaks (both brightening) at the Menzel gap KIC7180968 and KIC6366512. I remain unconvinced that KIC9909362 shows any structural break and the apparent dimming over the century is questionable given the raw data.
      3. Hippke then implies that, given that structural breaks at the Menzel gap that exists for KIC7180968 and KIC6366512, the structural break for KIC 8462852 is due to a data artefact (telescopes, emulsions, etc). If KIC7180968 and KIC6366512 both showed a dimming at the Menzel gap I would agree, but as both show a brightening we should be even more surprised that KIC 8462852 shows dimming at this point. Rather than eliminate the structural dimming significance Hippke should have recognised that KIC 8462852 is not behaving like other nearby F stars during the Menzel gap.
      4. Hippke then goes on to make the conclusion that “Assuming that no
      long-term dimming is present, the puzzling day-long dips
      in KIC8462852 might indeed be the result of a family of
      large comets”.
      There appears no justification to this conclusion given that KIC8462852 has dimmed at the Menzel gap, other nearby F stars have brightened at the Menzel gap and the “swarm of giant comets” is recognised as a poor explanation of the observed Kepler light curve.

      Looking forward to Dr Schafer’s response to the updated paper.

      • Harry R Ray February 12, 2016, 10:28

        Correct me if I am wrong, but I think what you are trying to say here is: SOME dimming between 1890 and 1989, but NOT linear and NOT 20%TOTAL. However, the dimming is SIGNIFIGANT ENOUGH to EXCLUDE comets as the LIKELY solution

        • Rafik February 12, 2016, 16:54

          My interpretation of the DASCH data for KIC8462852 is:
          1. I see no significant dimming apart from during the Menzel gap
          2. The “structural break” dimming that occurs during the Menzel gap is around .088 mag ( close to 10%) and may or may not be due to the effects of changes that occurred in data collection (eg use of telescopes. emulsions, etc). This needs to be checked by analysing the Sonneberg plates.
          3. In my opinion a “swarm of giants comets” is a poor explanation of the Kepler light curve. The dimming witnessed by Kepler is too complex and has too many different features for a simple explanation like comets.

        • Rafik February 12, 2016, 17:09

          I would also add that I have significant reservations about the use of the early DASCH data (first decade or so) in any analysis of long term light curves as the early data appears to be of poorer quality and there are fewer observations.

          • EricSECT February 13, 2016, 15:50

            OK, now the “Menzel Gap” is really starting to bother me. Most likely….. Something in our monitoring, and not the star, has changed. There were another set of plates (Sonnenberg?): has anyone looked at those?

            • Paul Carr February 18, 2016, 11:39

              Schaefer told me that he wanted to get access to the Sonnenberg plates.