The Story of Tabby’s Star: “The Most Mysterious Star in the Galaxy”

Asher Isbrucker
30 min readNov 12, 2018

A couple years ago, a few amateur astronomers digging through a trove of Kepler data made a peculiar discovery: it was a misbehaving star in the constellation Cygnus; one which erratically dimmed in unpredictable and unprecedented ways. They flagged the star, which perplexed astronomer after astronomer and became a media sensation when whispers of Dyson spheres and alien technology began to circulate. Much of that hooplah has faded away now, as the star and its mysteries have largely been explained, but the story of KIC 8462852—colloquially known as Tabby’s Star—is one to remember.

The following is a transcript of the podcast episode.

In 1967 a team of PhD students at Cambridge University finished building a telescope. It was a radio telescope, meant to search for and research mysterious objects in the sky called quasars.

Quasars were a recently discovered phenomena at the time. Strange radio frequencies coming from space. The word “quasar” comes from “quasi-stellar” — kind of star-like. They looked like stars, but didn’t act like stars. For a brief time when they were discovered in the 1950s, people thought they were signals from aliens. The Byrds even wrote a songabout them.

Quasars didn’t turn out to actually be aliens of course. But they were still really mysterious. Scientists didn’t reach consensus about what quasars were until the 1980s. They turned out to be objects at the center of galaxies surrounding supermassive black holes. So in the 1960s quasars were still fresh, they had no idea what they were looking at. And that’s why those students at Cambridge were building the radio telescope: to look at quasars.

Radio telescopes don’t show an image like a regular backyard telescope. Instead, they look for radio frequencies, which show up as black scribbles on long sheets of chart paper. The Cambridge telescope produced 96 feet of these scribbles per day.

One of the PhD students who worked on the telescope was named Jocelyn Bell Burnell. It was her job to analyze those 96 feet of scribbles by hand. Late one night, Jocelyn came across what she called a bit of “scruff” in the data — an anomaly which appeared as a regular pulse, up and down every 1.33 seconds. It wasn’t a quasar. It was something else. It looked almost like a beacon, and it seemed to be coming from a single point in space.

Jocelyn and her team were perplexed. The signal looked man-made, but it couldn’t be. No star was known to behave like this. It wasn’t radio interference from Earth, that was ruled out. Yet it pulsed with perfect clock-like regularity.

There was, of course, the elephant in the room: what if this signal was made by somebody else? The team didn’t really believe they were seeing a signal from an alien civilization, but couldn’t prove that they weren’t. In an homage, they dubbed the object LGM-1 — the LGMstands for Little Green Men.

It wasn’t long before Jocelyn found a similar signal coming from a different patch of sky. And then another, and another, and another, begging the question: what are the odds that if this is ET, they’re showing up the same way in a bunch of places at once?

As you can guess, they weren’t looking at aliens. What they were looking at were fast-spinning, ultra-dense stars, like cosmic tops — a new class of astrophysical object. They called them pulsars, referring to the pulse of the signal, like a heartbeat — except, in this case, devoid of life.

The pulses Jocelyn detected in 1967 are often considered one of the most suggestive of an alien source ever detected.

Looking back, it’s difficult to understand that they had no idea what they were looking at. During that brief window in 1967, for all they knew, they could be gazing at the answer to one of life’s greatest questions — blinking at them from space in perfect, clock-like intervals.

In the time since her discovery, Jocelyn has become a highly respected astronomer. In a 1999 interview with NASA, Jocelyn was asked what surprises her most about the universe.

Jocelyn Bell Burnell: I think what surprises me most are the surprises, the discoveries that are unexpected. The results that suddenly turn the tables on what we previously understood. The surprises keep rolling in, in a quite dramatic way, and that’s I think what surprises me most: the uncertainty about astronomy.

The uncertainty about astronomy. The surprises. They certainly do keep rolling in.

The reason I told you this story about the discovery of pulsars is because it closely echoes a story that’s unfolding right now in astronomy — the story of Tabby’s Star.

The star is named after Tabetha Boyajian, post-doctoral fellow at Yale University.

Tabetha Boyajian: My dream come true. I got a star named after me. And it’s a weird one!

She first saw this star years ago.

TB: When it was passed to me I was like “what’s this?” And I was like, I have no idea. And there were a couple other people there with me and I showed it to them and they were like “I don’t know, that’s weird!” And I think over the years, nobody has anything to say other than “That’s very… peculiar.” At least 100 professional astronomers have seen this light curve and couldn’t attribute it to anything we know of.

But it’s not Tabby’s Star itself that’s peculiar. As far as stars go, it’s rather ordinary. What’s so perplexing is what’s around Tabby’s Star. There’s something there — orbiting — and we have no idea what it is.

If you follow space news, this story may sound familiar to you. It was big around the end of 2015.

AI: I saw Neil Degrasse Tyson talking about it on the Tonight Show?

TB: Yeah, yeah, it was on SNL, it was kind of all over the place. It was very overwhelming.

Stephen Colbert: Let’s talk about something that’s got a lot of people excited right now, there is a star out there: KIC8462852.

News anchor: and we have this telescope that’s been staring at it for a number of years,

Neil Degrasse Tyson: with one purpose in mind: to find earth-like planets orbiting sun-like stars.

News anchor: but scientists say something strange keeps getting between the telescope and the star, they can’t figure out what it is.

NDT: well it’s got stuff we don’t know what it is.

SC: It’s dimming by 22%, not 1%, it’s a big dip and it happens frequently.

NDT: We don’t know what it is.

Michio Kaku: This could be the biggest story of the past 500 years, or it could be the biggest wild goose chase since the Loch Ness monster.

Most of that hype came from an article published in The Atlantic called “The Most Mysterious Star in the Galaxy.”

Ross Andersen: I guess I thought “oh this will be a nice hit for the week,” I did not expect it to be on SNL, the Tonight Show that very weekend.

This is the guy who wrote that article.

RA: I’m Ross Andersen, I’m a Senior Editor at the Atlantic. I write about science and technology and health mostly, and I have a sort of a thing for the space sciences. I’ve done some high impact stuff before, never seen a reaction like that, millions of people read the Atlantic story, untold numbers I suspect read stories that covered it. So strange to be a part of firestorm like that to say the least.

There could be many reasons why this story drew the attention it did, but there’s one clear reason above all others: someone said aliens.

We’ll get to that. But first, let’s rewind to a simpler time, before SNL and Late Night and the Atlantic article. Back when Tabby’s Star was simply another quiet, scintillating point of light hidden in the night sky.

NASA Announcer: 7, 6, 5…

Our story begins on March 7th, 2009, with the launch of a NASA mission called Kepler.

NASA Announcer: Engine start, 1, 0, liftoff of Delta 2 rocket with Kepler, in search for planets in some way like our own.

As the announcer guy said, Kepler’s mission was to find planets around other stars, called exoplanets. Kepler looked at over 150,000 stars in a section of space called the Kepler field, it’s a small square of space near the constellation Cygnus, and it measured their brightnesses for almost four years, looking for what astronomers call transits.

TB: That’s like a decrease in light, when a planet goes in front of the star.

A transit causes a tiny dip in the apparent brightness of the star. Every few months we download all Kepler’s data and plot it out and end up with a light curve — that’s a measure of a star’s brightness over time.

This is where astronomers look for those transits. So every time a planet passes in front of a star, it gets just a bit dimmer, and that causes a dip.

Kepler collected over 150,000 light curves, including Tabby’s Star. Computers did most of the leg-work, they can look through and pretty reliably find these transits which indicate exoplanets, but there was still the chance they’d missed something. Remember when Jocelyn had to go through the 96 feet of chart paper by hand? That’s because humans are better at finding visual patterns than computers are. And that’s what we’re looking for here: recurring, small dips. Astronomers wanted human eyes to look through the data as well, just in case, so they reached out to the public — regular plebeians like you or me — to help classify Kepler light curves and find exoplanets. They called the program Planet Hunters.

TB: It’s crowdsourcing. You don’t need to know anything to do this kind of thing, my son does it he’s six. I think he thinks he’s gonna find a planet across the screen at some point.

Darryl LaCourse: I don’t think there was much expectation at the beginning that we’d find any planets that supercomputers missed, but in fact we did actually.

This is Daryll LaCourse, he’s a Planet Hunter.

DL: You know embarrassingly they call me an amateur astronomer, but I live in Seattle and I don’t actually own a backyard telescope right now.

AI: That’s all you need!

DL: Right, so I like to flippantly joke that I just borrow a telescope in space and it works a lot better.

Now most of the light curves the Planet Hunters look through are normal, there’s nothing there, not even an exoplanet. Once in awhile if they’re really lucky, and this is rare, they’ll find recurring dips that indicate an exoplanet. It’s even rarer to find one the computers missed. But there’s one light curve among all the 150,000 that Kepler looked at, which is just totally unique. There’s nothing else like it. And that’s the light curve for Tabby’s star.

DL: It seems like a long time has passed now since the original Kepler mission ended and we never forgot about this light curve, I don’t think any of us on amateur side ever expected it’d be the most interesting light curve we found.

The light curve of Tabby’s Star is Exhibit A. It’s inexplicable. And it’s the crux of this story — the smoking gun.

AI: What exactly, when you look at the light curve, what’s so weird about it?

TB: Well Kepler observed it for 4 years, and for about 95% of the time it’s completely flat.

In other words, totally ordinary.

TB: But for the other 5% of the time it goes, it drops in brightness in a couple of different ways.

The dips in the light curve are measured as a percentage of the light that they block out. Planets cause small dips, usually lasting a few hours. Jupiter, for example, would cause a dip of around 1%. What they find with Tabby’s Star are these massive dips — up to 20%, lasting for days and weeks, not hours.

There are two big dipping regions — one halfway through and one at the end.

TB: The one halfway through lasted for about a week,

It shot down in a sharp spike then gradually returned to normal.

TB: and that’s all it consisted of, very smooth, lasted for about a week, and that was it. And then the ones at the very end, 2 years later, they’re asymmetric, very sporadic and ragged, whole lot of ups and downs, and the whole period lasts for almost three months.

Bizarre, and clearly not planets. Then, just as things are getting interesting —

TB: Then the Kepler spacecraft dies, so we don’t have more observations of it, which is a bummer, so we don’t know what happens then, but it was getting really really interesting at the end.

Two of Kepler’s reaction wheels broke, which meant it couldn’t keep steady in orbit. Good news is, after some down time and a lot of head scratching, NASA and some genius engineers managed to salvage the mission and resurrect Kepler as K2, a new mission, a phoenix from the ashes.

TB: I’m glad they did it, cause they’re still taking some great data, still finding new planets in different fields.

Except, the catch:

TB: We can’t look at the Kepler field anymore.

AI: So you can’t see this star anymore?

TB: We can’t look at the star anymore.

Yeah, bummer. So Tabby’s Star has again slipped out of sight. Which sucks because it was just getting good — and also because Tabby and her team need more data. All we have are the four years of Kepler data, which raise more questions than they answer. Without more data, we’re in the dark.

I spoke with one of Tabby’s colleagues, Jason Wright, assistant professor of astronomy and astrophysics at Penn State. He and Tabby have been working closely together on trying to figure out this star. When I asked him what could be causing it, he broke it down for me:

JW: I think we both have two categories of explanations for what’s going on, we have the good ideas, the good explanations, and bad explanations, and the good explanation column is empty. We just don’t have any good explanations. The bad explanations all don’t work in some way, and so we rank by how implausible they are, because they’re all implausible, or impossible.

The first idea, of course, is that there’s something wrong with the data.

TB: There’s gotta be something wrong with the telescope here. So what was really comforting is I went to a workshop for the Kepler space telescope in November. I talked to at least a dozen people there and they were like, “The data is good, we looked at it and it’s good, don’t worry.”

That was ruled out pretty quick. They’ve exhausted all the obvious bad explanations by now: giant planet, it can’t be a giant planet.

DL: You can’t have a single object blocking 20% of a star’s light and have it be a planet.

Orbiting star?

JW: Now sometimes other stars pass in front of the star, a binary system two stars orbiting each other, and that can cause big dips, cause the star can block most of the other star, so you can see it get 20% dimmer, but those are very regular, every time the star goes around you see it get dimmer again, and those have very characteristic patterns and this didn’t look anything like any of those.

Accretion disk?

TB: If you have a disk of material around a star, it will glow from the starlight heating it up. We see nothing like this. Once you’ve ruled that out it gets really tricky.

Dust cloud?

JW: There isn’t any evidence of a cloud there.

Pulsations, starspots, polar spots, black hole discs — for various reasons none of these seem to cut it.

JW: And that’s the thing, Dr. Boyajian worked for four years to study this thing, to find something extraordinary about it, anything that might explain these light curves, and everything about it’s totally normal! It’s not young, it doesn’t have a disk, it’s not spinning too fast.

TB: It looks normal any way you look at it.

JW: It’s just an ordinary star.

So far only one theory has stuck.

JW: Dr. Boyajian eventually landed on hypothesis that it’s a giant swarm of giant comets,

TB: that are coming into the star and blocking out the light. These are huge comets. Very, very huge comets. This is one of the reasons why people say “I don’t think so” because that would take a whole lot of comets, huger than anything that we have in our solar system by many factors of ten, it’s just not reasonable. But we don’t know what’s around other stars. It is kind of a stretch but it’s the best guess that we had on what it was.

But Tabby still had a paper to write.

TB: It was probably the hardest paper I ever wrote, there were so many people involved in so many different parts. We’re not trained to report something that’s not a conclusion. We’re trained to do an experiment, present your data, and this is your conclusion. This had you know, we have a good idea what this is?

In her paper, she presents her findings and essentially concludes that we need more data to reach a conclusion.

There is one explanation, however unlikely, that Tabby didn’t mention in her paper. In serious astronomy it can be an icky topic, and also hard to prove.

SC: Right, and one thing that’s been thrown out there, have you heard about this Seth?

Seth MacFarlane: Yeah, yeah. They think it’s the Borg.

SC: They’re saying alien megastructure might be one unlikely but possible answer.

NDT: Excuse me?

TB (TED): Now, you may be wondering, OK, Tabby, well, how do aliens actually explain this light curve?

This is an excerpt from Tabby’s TED Talk about the star.

TB (TED): OK, well, imagine a civilization that’s much more advanced than our own. In this hypothetical circumstance, this civilization would have exhausted the energy supply of their home planet, so where could they get more energy? Well, they have a host star just like we have a sun, and so if they were able to capture more energy from this star, then that would solve their energy needs. So they would go and build huge structures. These giant megastructures, like ginormous solar panels, are called Dyson spheres.

Dyson spheres might sound like science fiction, but they fit the predicted path of what advanced civilizations might build. It’s possible.

JW: In 2005 an astronomer named Luke Arnold pointed out that when Kepler was up there looking for planets passing in front of stars, it would also notice if these things existed and it would be sensitive to them if they were passing between the Earth and the star. And he showed that Kepler would probably tell the difference between a planet and a giant structure of some kind, so he said we should be on lookout for things passing in front of stars making them dimmer that aren’t planets, and don’t look like planets, and are otherwise inexplicable.

Sound familiar?

JW: So I had that on my mind, and I was in fact trying to write up a paper that argued that Kepler didn’t see any of those,

But then came Tabby’s Star.

JW: I couldn’t say that Kepler didn’t find any giant alien megastructures until we figured out what’s going on with Tabby’s Star. So when she showed it to me, I thought shoot, I can’t write that paper that I was going to write saying we hadn’t seen any of those things. Now we have to solve Tabby’s Star so I can finish this paper that says we didn’t find anything.

The whole dyson sphere hooplah is the reason this story attracted so much attention. Just search Google Images for “Tabby’s Star” and you’ll see what I mean.

TB: It’s fun to think about, and it definitely gets people excited, it wasn’t what we were out to do in beginning but it’s definitely got a lot of people excited about it, it got a lot of astronomers excited about it too which ended up being good for us, because we got a lot more data when it came in. But talking to hundreds of reporters trying to get the story straight that we’re not Skyping with aliens on Friday night, cause I was getting phone calls all times of night just, “So you’re talking to aliens?” No! But you feel you have to answer all these, otherwise they’re going to assume the most exciting story, it just takes off and gets out of control.

JW: I think the problem is when the media runs away with it, and it gets completely overhyped just because someone said aliens. So the lesson is don’t use the word because if a reporter hears you say that, it’s gonna be off everywhere and everyone’s gonna have to answer questions about why it’s not aliens, and everything, so that’s a danger, I don’t know if it’s possible to train the media that just because someone said that that it’s a big story,

The dyson sphere hypothesis is exciting to think about,

TB: but we don’t know anything about what a megastructure would be like? I definitely would be into caution about taking anything seriously about something like that does exist until we find actual evidence of some kind of sign that it isn’t something natural.

If you’re going to seriously consider extraterrestrial intelligence as a hypothesis, you have to see a signal. With this in mind, Jason reached out to an old colleague of his:

AS: He contacted me and said “If I had an interesting candidate for a SETI search, what would I do?”

This is Andrew Siemion.

AS: I’m the Director of Berkeley SETI Research Center at the University of California at Berkeley.

Jason and Andrew got to talking about this star as a potential SETI candidate.

AS: Eventually got to point where he wanted to write a proposal.

JW: Just in case, just to check, because it’s the weirdest thing out there.

The best telescope to use would be the Green Bank Radio Telescope in Virginia. It’s the Rolls Royce of radio telescopes. It’s huge, the biggest moveable land object in the world at over 100m in diameter, and it’s located in the United States National Radio Quiet Zone in Virginia, where radio frequencies are restricted to allow for good quality observations. So it’d be perfect, and they wrote up a proposal.

TB: I was hesitant at first, cause I thought this is gonna put a black mark over my name, “This girl’s crazy she doesn’t do serious science,”

Despite hesitations, they submitted their proposal, and expect to begin observations in October of this year.

There are a number of ways to look for extraterrestrial life on other planets, depending how close we are. We can take samples or analyze the atmosphere for chemicals that suggest life (oxygen and methane are prime suspects). But most exoplanets are too far away for that, so we rely on SETI.

AS: We don’t have any way of detecting intelligent life per se, but we can detect technology, and if we detect an ET technology we can assume there is some intelligent life that created that technology.

AI: Would it be fair to call astrobiology something of a blind science because there are so many unknowns?

AS: Well, I think there are aspects of it that are very concrete. The elephant in the room, maybe this is what you’re alluding to, is that we only know of one example of life anywhere in universe so astrobiology is in some sense inherently a speculative field, because we don’t really know whether that exists, so for now I guess there is an inherent speculation, but perhaps in a few decades or maybe even less the field of astrobiology will change very much from one in which it’s inherently speculative to one in which we know for certain that life exists elsewhere.

AI: Yeah, I guess we have no choice but to search for life as we know it because it’s the only example we have.

AS: Yeah I think that’s right, the nice thing about SETI, if I could stand on a soapbox for a minute, is the kind of searches we do are agnostic to the type of life that created the technology, it might be carbon based like us, it might be silicon based life, it might be artificially intelligent life, it could be anything, but we assume that other intelligent life will have same use for electromagnetic technology as we do. The kind of technology we look for is independent of the type of life. I think people that look for simple life, or dumb life as we sometimes like to call it, they have a harder job because they can only search in most cases for life that looks like the kind of life we have on Earth.

There are so many hypotheticals to consider when looking for alien life. We don’t know how it would manifest itself, how they’d behave — the whole idea of a dyson sphere is just that — an idea, a hypothetical, a concept. Really, who knows how aliens would behave, or what they’d build. What if they don’t follow the same rules of life as we do? And what if they don’t even use the kind of technology we’re looking for? You can’t rule it out. And that makes a bad hypothesis.

JW: The problem with invoking aliens to explain things is it’s not predictive. If they’re giving off radio transmissions then we can look for those, so we should check, we should totally check, we should absolutely look because it’s the best chance we’ve got in that avenue. But we don’t know what aliens would do, we don’t know what advanced civilizations, why they’d build giant solar panels, we could guess, we don’t know how big they’d be, we don’t know how far from the star, we don’t know how many they’d build, we don’t know how fast they could build them, it’s not predictive. So if you say maybe it’s aliens, okay, so now what? How do you confirm that? I don’t know. And so that’s the problem with the alien hypothesis; you can always dream up something, and say sure, why not? They have physics we don’t know about, that’ll explain anything.

AI: They did it in Star Wars, why couldn’t they…

JW: Right, sure, maybe it’s Starkiller base, draining the star and making it dimmer, why not? Okay? But what do you do with that? You can’t do much with that. So that’s why the route to exploring the alien hypothesis is to look for unambiguous signs of intelligence, radio communication, laser communication, we can try that, and you’ve gotta look somewhere, so you might as well look at the weird star, and then on the natural side to figure out as much as you can about what it isn’t, what natural thing it isn’t. You can’t prove it’s aliens until you see a signal. Short of seeing a signal with SETI all we can do is pursue natural hypotheses, which is great because it’s a really interesting scientific target on the scientific merits, so all the astronomers that are trying to understand this star, are in a sense doing SETI in that they’re doing the only thing you can do to show it’s aliens, which is to rule out every possible natural explanation. Now, that’s a really long road to hoe, who knows, that could take forever, but the more natural explanations we can rule out, the more mysterious it becomes and the more we can bring to bear on the star to figure out what’s going on.

Bottom line is, if we have a hope of finding alien life, an interesting candidate — a mystery wrapped up in an enigma — we might as well try. Even if it takes an optimist.

AI: Like you said before, the odds that you’re gonna find ET are super low, so do you find that discouraging?

AS: Well, we don’t really know what the odds are. Different people have different guesses about the estimates of the prevalence of technologically capable life elsewhere in the universe. But you’re right, it does take an optimist, or at least someone that doesn’t easily get discouraged to work in SETI. My particular view on this is it’s such an incredibly fundamentally question, are we alone as intelligent beings in the universe, that it’s worth continuing to work on, and continuing to try hard at answering that question regardless of the fact that you might get a little discouraged. Every time I get even the littlest bit discouraged I step back and think to myself that the work I’m doing is potentially going to be responsible for most profound, fundamental discovery in the history of human discovery. There is not a greater question that can be asked in my view. If you think about it that way, it’s easy to get your spirits up again.

I should mention here that an initial SETI survey in October 2015 came up empty. It doesn’t mean there’s nothing there — a follow-up survey with the Green Bank telescope will confirm that. And, again, even if they don’t find any signals, that won’t stop some people from persisting that this is a dyson sphere built by aliens — and that can’t be ruled out.

Okay, so quick recap: In 2009 Kepler launches to look for exoplanets around other stars. So it’s looking at all these stars, it finds one star exhibiting a strange light curve. Astronomers are stumped, there’s no known explanation, it’s completely unprecedented. Hypothetical alien megastructures come up as a possible explanation, and SETI is set to investigate.

But there’s one more thing. Just when this star seems as strange as it can get,

JW: Finally, it did something else weird, or it was discovered to have done something else weird. There’s an astronomer at Louisiana State University named Bradley Schaefer and he wanted to know if this had ever happened before, and he remembered the plate stacks at Harvard College Observatory.

I called Dr. Schaefer up to talk about what he found. Just a heads up the audio quality isn’t too great here.

BS: Hey, my name is Brad Schaefer, I’m a Professor in the Department of Physics and Astronomy at Louisiana University, I spend a lot of time looking at old astronomical photos of the sky I should say, that can give you a long history of what a star has been doing for the last, well more than a century. I heard about Tabby’s Star the way everyone else did. A friend came up and said “Hey, have you heard of this star? It is weird.”

And so he ponders it for awhile, and then he thinks:

BS: You know, I wonder, well Tabby only has data to back to the time of the launch of Kepler, which is I think 2009, and I wonder what Tabby’s star was doing before 2009, where can I get the answer to that question?

Fortunately, some astronomers began photographing the night sky over a century ago. The photographs are negatives preserved on glass plates,

BS: and so it turns out the sky background is mostly clear, and the stars appear as black dots of varying size, and so the brighter the star larger the dot, and the fainter star, the smaller and fainter the dot. The majority of these old photographic plates happen to be at the Harvard College Observatory in Cambridge, Massachusetts.

The Harvard Collection contains photographs dating from 1890 to 1989.

BS: So I have a full hundred years of data, so even now I can go back and look at what the brightness of star was in 1890.

So he thought:

BS: I’ll be at Harvard in a week or two, I’ll just go check to see what the star was doing.

So he goes to the Harvard archives and pulls out these photographs, and starts to do his thing.

BS: You have good measures of how bright Tabby’s Star is over the last century,

And what he finds is astounding.

BS: and what I find is Tabby’s star is fading, it’s getting dimmer. It’s roughly 20% dimmer in 1989 than it was in 1890, so it’s dimmed by 20%.

JW: And stars don’t do that! This is just not something stars do, they don’t get dimmer, when they run out of hydrogen at the end of their lives, over a millionyears or more, they’ll get brighter actually, as they run out of fuel, they don’t get dimmer over 100 years.

BS: There’s no precedent for this, nobody’s every seen anything like this, there’s no theoretical understanding of this.

JW: And so this is now the second unprecedented change in the star’s brightness that’s been noticed.

BS: Tabby’s star is doing something that ordinary F type main sequence stars are not, should not be doing, they should not be dimming by 20% on the time scale of century.

A recent follow-up corroborated Dr. Schaefer’s findings, showing that Tabby’s Star also dimmed by 3% in its overall magnitude over the course of Kepler’s four-year observation — so, again, this likely wasn’t a misread of the data. This is actually happening. Tabby’s Star is dimming.

JW: That’s when we went to the column of bad ideas and started erasing things too bad to even be on the list. Then we started putting things on the list to explain the dimming. You can kind of work your way into some ideas of why it got dimmer over 100 years, and they’re really implausible, but what about the Kepler data? What’s with the short term big dips? And you realize your model doesn’t explain those at all. Dr. Schaefer said whatever’s causing one of these effects is probably causing both. It’s unlikely that it’s doing two unprecedented unique things at the same time.

BS: Well Occam’s Razor comes back and says the simpler answer is probably, is more likely, to be correct. So we can come to at least a very likely conclusion that there’s only one mechanism involved for the Harvard dips and the Kepler dips, and that doesn’t mean we know what that mechanism is, but they’re probably the same.

TB: And so this really makes it tough, if we had more data, and this is a ton of data that we have, and amazing quality, but you know knowing when it’s gonna dip again, what do these dips look like, how long do they last, any of this, will help us figure out what it is.

Without more data it’s difficult to predict the next dip. So in order to solve the riddle of Tabby’s Star, we need more data.

BS: One of the things you have not come back and asked me yet is “How are we going to solve this question of Tabby’s Star?” And here I can actually give you my best guess of how we’re going to go solving it. I think what is needed is going to be catching Tabby’s Star going into a dip, now the trouble with that is we have to get an alert to know when Tabby’s Star is in dip, so somebody can go and get a spectrum of it.

TB (TED): But professional astronomers like me, we have limited resources for this kind of thing, and Kepler is onto a different mission.

It’s notoriously difficult and competitive to get any time on professional astronomical telescopes.

BS: So what you need is system by which people are continuously monitoring Tabby’s star, waiting, waiting, waiting for it to go into a dip, and then you immediately alert the world, and then someone will go off and take a spectrum.

Tabby and Jason launched a Kickstarter campaign to fund continuous observation of the star by a private network of telescopes.

TB (TED): And I’m happy to say that once again citizen scientists have come in and saved the day.

They surpassed their goal, which means that whenever the star goes into the next dip, it won’t do so in the dark.

TB (TED): Amateur astronomers with their backyard telescopes,

BS: doctors and lawyers and firemen and nurses, and everything else,

TB (TED): stepped up immediately and started observing the star nightly at their own facilities.

We’ll have countless eyes on the star, ready to record what happens next, and hopefully, finally, shed some light on what’s going on.

JW: So we have a lot of telescopes on standby just waiting for the call.

BS: There’s reasonable chance that we could catch Tabby’s Star in a dip coming up tonight, or maybe next week, or maybe next month. And when it goes faint, they’ll notify the AAVSO who’ll then notify Tabby who’ll then notify the world,

JW: Then we can throw everything we’ve got at it.

DL: And they’ll go look at the star while this dipping is occurring.

BS: And she has telescopes lined up which will then upon alert take a spectrum of Tabby’s Star.

DL: So we’ll look at it in the infrared, X-ray, UV, the whole spectrum.

BS: Catching a spectrum of this star during a dip probably will be the breaking case, we’ll be able to say “Oh, that’s what it is, it’s such and so,” and then we’ll go work out the details.

JW: And then we’ll be able to figure out exactly what’s between us and the star.

DL: If we don’t go look, we’ll never know.

BS: The sky is full of stars, and astronomers have a hard time exploring all of them, and when you start looking at things closely, you start coming up with these anomalies and things that are whacko weird, and so on that level Tabby’s Star is just one of a long succession of stars in the sky which at the time we first discovered we didn’t really know what they were doing, many of those we have since understood, some of them we haven’t, and they’re just there we have no idea what to make of them, and they’re something new, and that’s what Tabby’s star is now, we have no idea what’s going on, and we still don’t.

DL: This is why we do this, to explore and discover, and we have to be prepared for unexpected results.

JW: There have been a few times in astronomy when the column of good ideas was empty for so long that astronomers said you know, maybe we need to consider the extraterrestrial intelligence hypothesis.

DL: Say this goes down the way pulsars did, and there’ll be a footnote that “they thought it was little green men but it was just a strangely behaving star,” well this wasn’t the first time and it certainly won’t be the last.

JW: But it’s following the same progression in terms of we don’t know what it is, the alien hypothesis comes up, it’s grabbed the public’s attention, and now we get to figure out what’s really going on. It’s hard to imagine it being nearly as amazing an object as pulsars or quasars, but there’s something going on, and as a stellar astrophysicist I’m really interested to know what this star is doing.

TB (TED): Personally, as a scientist, my money is on the natural explanation. But don’t get me wrong I do think it’d be awesome to find aliens. Either way, there’s something new and really interesting to discover.

RA: Look, there’s clearly something very strange going on around that star, but in all probability it’s nothing to do with extraterrestrials. And yet, to me one of the bigger stories there and I’m always shocked that it hasn’t fully penetrated the public consciousness, is the Kepler space telescope and that whole mission. My sense is that when people look back on the 21st century, 100, 200, 300, 400, maybe even thousands of years from now, one of the things they’re going to remember is the Kepler mission, and this extraordinary moment in the history of ideas when people discovered that there are planets around nearly every star in the galaxy.

TB (TED): What’s amazing to me is that this star would never have been found by computers because we just weren’t looking for something like this. And what’s more exciting is that there’s more data to come. There are new missions coming up that are observing millions of more stars all over the sky. And just think, what will it mean when we find another star like this? What will it mean if we don’t find another star like this?

Enigmas like Tabby’s Star, quasars, and pulsars remind us of the questions we don’t even know to ask, the unknown unknowns, the surprises. Inherent in science is a tantalizing uncertainty; that the knowledge we desire may perpetually remain just beyond reach — like a carrot on a string.

BS: Yeah, and Mother Nature is not out there trying to help us, we’re trying to understand mysteries of Mother Nature and she’s under no obligation to help us out, so right now we don’t have any good ideas, but you keep putting the time into this because you know there is something weird and whacko and unique and new down the road, and maybe Tabby’s Star is this too.

AI: Is that what you’re hoping for?

BS: Well of course we hope for it, but my hopes don’t matter.

AI: Right, it just matters what the truth is I guess.

BS: Exactly, that’s what we’re doing. Astronomers and scientists, we are driven by reality, we want nature to tell us what reality is, not what our hopes and desires are. We are an evidence-ocracy, we are driven by evidence, if the idea doesn’t match the evidence, then it’s not a good idea.

AI: At this point, a few years in, are you getting sick of this star?

TB: Well I have love hate relationship of it. I wouldn’t say I’m sick of it, it’s definitely exciting, and I now have my own Wikipedia page, as you said, that’s pretty cool, I don’t know who invented that, but that was like, whoa! But it’s pretty awesome how something like this, and I would never have expected it, can get the whole world interested in astronomy again. People are out in their backyard with telescopes, simple camera equipment, that sort of thing, they can do this photometry for this star and get useable data. And so the AAVSO has set up a website that makes it fairly easy to upload your data, and so I go on there daily to check okay what’s the star doing, okay nothing good I don’t have to do anything, just preparing.

AI: Getting ready for that dip again.

TB: Yeah, it’s a career project, I don’t know how long it’s gonna be.

AI: Could be years, could be a decade, maybe this year you get data again.

TB: That would be excellent, yes.

It’s fitting that Tabby’s Star is invisible to the naked eye. It forces is us to take a closer look, and reminds us that in the cosmos, not everything is as it seems. Behind the scintillating stars and shrouded in the darkness between are the surprises — the unknown unknowns — waiting to be discovered.

Now if you want to participate in real scientific research, go check out Planet Hunters at

Tabby’s Star was brought to the attention of astronomers by Planet Hunters, a number of whom are credited as co-authors on Tabby’s paper about the star — so it’s truly real science you’re contributing to. Quick shout out to a few Planet Hunters in particular who first flagged Tabby’s Star as strange: Andrew Szewczyk, Sam Goodman, and Abe Hoekstra.

If astronomy isn’t really your thing, there are lots of other projects you can participate in — arts, biology, climate science, history, medicine — all using the power of citizen science. One project I’ve been enjoying is Decoding the Civil War, transcribing real Civil War telegraphs. Go check them out —

This episode was produced independently by me, Asher Isbrucker.

I’d like to thank all of the people who gave their time and lent their voices for this episode: Tabetha Boyajian (@tsboyajian), Jason Wright (@Astro_Wright), Andrew Siemion, Brad Schaefer, Ross Andersen (@andersen), and Daryll LaCourse. Big thanks to all of you. Thanks as well to Professor Jaymie Matthews.

Music in this episode was by Lee Rosevere, Corsica S, Chris Zabriskie, Sergey Cheremisinov, Little Glass Men, Lee Maddeford, and Ketsa. You also heard excerpts from “CTA 102” by The Byrds, the X Files Theme, and the Late Show with Stephen Colbert.

If you want to follow dedicated news about the star updated by the team researching it, go to

Thanks, as well, to you — the listener. Whoever you are, thank you for lending me your ears. This is my second podcast episode and I’m still figuring this whole thing out — this episode was a tremendous challenge to put together, but I learned a lot in doing so. On to the next one.

Further information:

Planet Hunters credited with first flagging Tabby’s Star, setting this whole thing off: Andrew Szewczyk, Sam Goodman, and Abe Hoekstra.

Check out Planet Hunters & other citizen science projects

The official website for updates on Tabby’s Star

Tabby’s paper about the star

Ross’ Atlantic article about the star

And a follow up article

Tabby’s TED Talk about the star

Fact-checking Twitter account for Tabby’s Star