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

If you’re looking for a guide to this series, click here.

I’ve just re-submitted a paper, which I expect to be accepted soon in light of a very favorable and constructive referee’s report, about KIC 8462852.  It covers the puzzle as I see it now, the landscape of solutions—from the plausible to the all-but-impossible—and opportunities for future progress. I’m especially excited for the GAIA parallax, which will really help us to narrow things down!

So I’m going to slow-blog the paper over the next week or so, up until the day it actually appears on the arXiv (after it’s accepted).

OK, let’s go!

The Story So Far

Dr. Tabetha Boyajian (now an assistant professor at LSU) first announced KIC 8462852 to the world in a paper that described how it was discovered, how it is an apparently ordinary F star except for its bizarre series of photometric “dips,” and how hard she and her co-authors, including Prof. Saul Rappaport, worked to solve the puzzle.  I’ve blogged previously about the whole story, including the subsequent media coverage here, and you should read that to catch up if you’re not familiar with the star.  I also gave a talk about it that you can watch here:

Then Bradley Schaefer looked at old DASCH photometry and found that Boyajian’s Star has been fading over the past 100 years, a claim at least as extraordinary as the star’s Kepler light curve.  There was a lot of shouting over this claim, and whether it was right, which Kimberly Cartier and I documented in an article for the Atlantic, linked in this blog post.

Ben Montet, looking up, presumably at Boyajian's Star.

Ben Montet, looking up, presumably at Boyajian’s Star.

The big news recently is that Ben Montet & Josh Simon very cleverly recently used the Kepler full-frame imagery—some calibration data that doesn’t get much attention because you can’t use it to find planets—to get accurate long-term photometry of Boyajian’s Star over the course of the mission.  Amazingly (to everyone but Bradley, I suspect), they found that the star got 4% dimmer over 4 years, in a monotonic but irregular way.  What’s more it is the only star out of > 200 that show this effect.

In my opinion, this independent confirmation of the unprecedented effect Schaefer claimed—even if not covering the same time period—shows that Shaefer’s analysis is correct and the star really has dimmed a lot.  Adding the two effects, the star is now apparently at least 17% dimmer than it was in 1890!

Where We Are Now

So what the heck is going on?  We now have two inexplicable things going on: long-term, secular dimming of 17% in 115 years, and these days-long, deep “dips” of up to 22%.  Both are very hard to explain.

Well, Occum’s Razor points towards a single explanation for both the secular dimming and the dips. Of course, in principle they may be unrelated, in which case Boyajian’s Star is extraordinary for two independent reasons. But I favor explanations that could plausibly cause both.  At any rate, I’ve been engaging in a lot of “clean-sheet” reasoning lately, trying to cover all of the bases, and working with a lot of people to figure out what’s plausible.  Steinn Sigurdsson, my often-time theorist sounding-board, is a co-author.

We decided that the explanation for the dimming must occur either at Boyajian’s Star itself (intrinsic variability), in orbit around it (circumstellar material), between the Sun and Boyajian’s Star (interstellar material) or in the Solar System (either between us and the star or in our instruments).  In future installments, I’ll cover the observational constraints, including dip periodicities, long-wavelength constraints, and the brightnesses of nearby stars, and then go through each possibility and give it a plausibility.

Wait, What Did You Call the Star?

Prof. Boyajian, looking up, presumably at Boyajian's Star.

Prof. Boyajian, looking up, presumably at Boyajian’s Star.

I’ve decided to call it “Boyajian’s Star“.  Prof. Boyajian herself calls it the “WTF” star, ostensibly after the subtitle of her paper (“Where’s the Flux?”, natch).  Early on during the media firestorm, a reporter asked me what I call it, and I admitted I could never remember its phone number and that within my group we called it “Tabby’s Star,”  because she first showed it to us, back before it was published. The name stuck, and now that’s what it’s usually called.

I’m conflicted about that term.  On the one hand, it has ensured that Tabby gets the credit for her work establishing how strange the star is, which is great (I wish I could claim that’s why I first used the term! It’s certainly why I kept using it).  On the other hand, that name is actually the most common among professional astronomers, which is incongruous with other eponymous stars.  You see, there’s a long tradition of naming stars after the people who made them famous—Barnard’s Star, Kapteyn’s Star, Przybylski’s Star—but professionalism and formality dictate that we always use the namesake’s surname.  Not only does “Tabby’s Star” use her given name, it uses the diminutive form.  It reminds me too much of one of the sexist double-standards common in academia (e.g. a man is “Prof. Smith”, but a woman is “Jenny”, especially from undergraduates!)

So, I’ve decided that when it comes to the professional literature, I’ll follow tradition and call it “Boyajian’s Star”.  If other astronomers do the same, perhaps it will stick.

The paper is Wright & Sigurdsson, “Families of Plausible Solutions to the Puzzle of Boyajian’s Star,” and I’ll dribble out more about it in future installments until the arXiv posting.

Part II is here.

Update: By popular demand, Tabby has given us a pronunciation guide for “Boyajian”. She says “boy-AH-zhun”, with the j sounding like that in “Jean-Luc Picard” (that is, say “sh,” but use your voice, don’t whisper).

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

  1. Sion

    Considering your audience, I’d have gone with “boy-AH-zhun”, with the j sounding like the j in Jean-Luc Picard! ;)

    (Here in the UK we say azure kind of like ‘as you’re’. No zh sound.)

  2. Dennis M O'Callaghan

    As I’m sure you’re aware, names of celestial objects lie within the purview of the International Astronomical Union as a result of their persuasive authority among the astronomical community. The IAU’s Working Group on Star Names has been established to adopt new unique names for stars of scientific and historical value. You might therefore wish to take up your suggestions as to this star’s name with them!

  3. eric

    The lack of excess IR is strong support for an astrophysical cause for the dimmngs above all other plausible scenarios.

  4. Keith Henson

    I mentioned this a couple of times before.

    One of the weirdest things about this star is the lack of IR flux. If that continues to show up, it’s going to be hard to figure out a natural cause for something that blocks up to 22% of the light of the star and does not re radiate the energy as IR.

    However, it happens that a year or so before the announcement we published a power satellite design that radiate the waste heat anisotropic, solar north and south of the local ecliptic.


    The LEO to GEO transport method has been superseded, but current design is similar, with shades that prevent sunlight from heating the radiator tubes. The sunshades also shades block the IR from radiating in the plane of the ecliptic.

    Not saying we are looking at an alien megastructure just that there are imaginable structures that would not radiate IR in our direction. James Webb telescope is another structure that radiates away from the direction it is looking.

  5. jtw13 Post author

    Maybe, but it’s common to lay out the consequences of various outcomes of an experiment before the experiment is complete. It shows the process working, lets people document their ideas in advance, and allows for a more objective analysis of the results.

  6. larry

    The GAIA parallax data is just a few weeks away. Wouldn’t it be better to wait for that before publishing?

  7. jtw13 Post author


    I have always been OK with “Tabby’s Star” as a popular name (not least because Tabby’s OK with it!), but always felt that the professional literature maintains a level of formality and professionalism wherein it really needs to be “Boyajian’s Star.” Now that I’ve finally written a paper on about it, I finally have a chance to do something about it!

  8. jtw13 Post author

    I’m not sure how she says it.

    I think the 2nd syllable is stressed, and j is as in “azure”, so I say boy-AH-zhun or boy-AH-zhee-un. Internet is not in agreement on whether a Turkish/Armenian “j” is hard or soft, bit in the end I agree with you that it’s how she pronounces it that matters.

  9. Jeffrey Silverman

    Excellent recap of where we are with Boyajian’s Star and I look forward to reading the future blog posts. And as a long-time collaboration of Prof. Schaefer, I was personally pleased to see his work on this object vindicated.
    I’m mostly commenting, though, to commend your public correction of the name of this object. As soon as I saw your headline, I realized that Boyajian’s Star is obviously the correct name for this object given the history of and naming conventions in astronomy and that “Tabby’s Star” was less appropriate for a variety of reasons. One question I have about it, though, is what is Prof. Boyajian’s preferred pronunciation of her (and the star’s) name?

  10. Kimberly Cartier

    This is a nice start to a series of blog posts about this topic. I’ve had lots of conversations with people who have been struggling to keep all of the different ideas straight, and sorting out what’s plausible or not.

    I especially appreciate your remarks about appropriately naming the star, and I hope this catches on with others as well! It’s easy to forget or overlook these kind of double standards and I appreciate the effort that’s being taken to correct it.

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