The most mysterious star in the universe | Tabetha Boyajian

6,156,046 views ・ 2016-04-29

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Extraordinary claims require extraordinary evidence,
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and it is my job, my responsibility, as an astronomer
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to remind people that alien hypotheses should always be a last resort.
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Now, I want to tell you a story about that.
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It involves data from a NASA mission,
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ordinary people and one of the most extraordinary stars in our galaxy.
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It began in 2009 with the launch of NASA's Kepler mission.
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Kepler's main scientific objective
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was to find planets outside of our solar system.
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It did this by staring at a single field in the sky,
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this one, with all the tiny boxes.
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And in this one field,
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it monitored the brightness of over 150,000 stars
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continuously for four years,
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taking a data point every 30 minutes.
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It was looking for what astronomers call a transit.
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This is when the planet's orbit is aligned in our line of sight,
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just so that the planet crosses in front of a star.
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And when this happens, it blocks out a tiny bit of starlight,
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which you can see as a dip in this curve.
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And so the team at NASA had developed very sophisticated computers
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to search for transits in all the Kepler data.
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At the same time of the first data release,
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astronomers at Yale were wondering an interesting thing:
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What if computers missed something?
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And so we launched the citizen science project called Planet Hunters
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to have people look at the same data.
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The human brain has an amazing ability for pattern recognition,
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sometimes even better than a computer.
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However, there was a lot of skepticism around this.
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My colleague, Debra Fischer, founder of the Planet Hunters project,
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said that people at the time were saying,
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"You're crazy. There's no way that a computer will miss a signal."
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And so it was on, the classic human versus machine gamble.
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And if we found one planet, we would be thrilled.
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When I joined the team four years ago,
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we had already found a couple.
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And today, with the help of over 300,000 science enthusiasts,
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we have found dozens,
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and we've also found one of the most mysterious stars
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in our galaxy.
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So to understand this,
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let me show you what a normal transit in Kepler data looks like.
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On this graph on the left-hand side you have the amount of light,
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and on the bottom is time.
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The white line is light just from the star,
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what astronomers call a light curve.
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Now, when a planet transits a star, it blocks out a little bit of this light,
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and the depth of this transit reflects the size of the object itself.
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And so, for example, let's take Jupiter.
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Planets don't get much bigger than Jupiter.
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Jupiter will make a one percent drop in a star's brightness.
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Earth, on the other hand, is 11 times smaller than Jupiter,
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and the signal is barely visible in the data.
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So back to our mystery.
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A few years ago, Planet Hunters were sifting through data looking for transits,
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and they spotted a mysterious signal coming from the star KIC 8462852.
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The observations in May of 2009 were the first they spotted,
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and they started talking about this in the discussion forums.
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They said and object like Jupiter
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would make a drop like this in the star's light,
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but they were also saying it was giant.
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You see, transits normally only last for a few hours,
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and this one lasted for almost a week.
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They were also saying that it looks asymmetric,
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meaning that instead of the clean, U-shaped dip that we saw with Jupiter,
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it had this strange slope that you can see on the left side.
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This seemed to indicate
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that whatever was getting in the way and blocking the starlight
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was not circular like a planet.
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There are few more dips that happened,
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but for a couple of years, it was pretty quiet.
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And then in March of 2011, we see this.
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The star's light drops by a whole 15 percent,
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and this is huge compared to a planet,
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which would only make a one percent drop.
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We described this feature as both smooth and clean.
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It also is asymmetric,
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having a gradual dimming that lasts almost a week,
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and then it snaps right back up to normal in just a matter of days.
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And again, after this, not much happens
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until February of 2013.
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Things start to get really crazy.
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There is a huge complex of dips in the light curve that appear,
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and they last for like a hundred days,
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all the way up into the Kepler mission's end.
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These dips have variable shapes.
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Some are very sharp, and some are broad,
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and they also have variable durations.
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Some last just for a day or two, and some for more than a week.
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And there's also up and down trends within some of these dips,
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almost like several independent events were superimposed on top of each other.
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And at this time, this star drops in its brightness over 20 percent.
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This means that whatever is blocking its light
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has an area of over 1,000 times the area of our planet Earth.
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This is truly remarkable.
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And so the citizen scientists, when they saw this,
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they notified the science team that they found something weird enough
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that it might be worth following up.
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And so when the science team looked at it,
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we're like, "Yeah, there's probably just something wrong with the data."
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But we looked really, really, really hard,
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and the data were good.
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And so what was happening had to be astrophysical,
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meaning that something in space was getting in the way
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and blocking starlight.
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And so at this point,
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we set out to learn everything we could about the star
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to see if we could find any clues to what was going on.
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And the citizen scientists who helped us in this discovery,
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they joined along for the ride
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watching science in action firsthand.
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First, somebody said, you know, what if this star was very young
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and it still had the cloud of material it was born from surrounding it.
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And then somebody else said,
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well, what if the star had already formed planets,
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and two of these planets had collided,
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similar to the Earth-Moon forming event.
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Well, both of these theories could explain part of the data,
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but the difficulties were that the star showed no signs of being young,
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and there was no glow from any of the material
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that was heated up by the star's light,
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and you would expect this if the star was young
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or if there was a collision and a lot of dust was produced.
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And so somebody else said,
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well, how about a huge swarm of comets
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that are passing by this star in a very elliptical orbit?
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Well, it ends up that this is actually consistent with our observations.
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But I agree, it does feel a little contrived.
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You see, it would take hundreds of comets
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to reproduce what we're observing.
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And these are only the comets
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that happen to pass between us and the star.
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And so in reality, we're talking thousands to tens of thousands of comets.
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But of all the bad ideas we had,
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this one was the best.
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And so we went ahead and published our findings.
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Now, let me tell you, this was one of the hardest papers I ever wrote.
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Scientists are meant to publish results,
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and this situation was far from that.
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And so we decided to give it a catchy title,
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and we called it: "Where's The Flux?"
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I will let you work out the acronym.
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(Laughter)
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So this isn't the end of the story.
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Around the same time I was writing this paper,
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I met with a colleague of mine, Jason Wright,
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and he was also writing a paper on Kepler data.
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And he was saying that with Kepler's extreme precision,
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it could actually detect alien megastructures around stars,
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but it didn't.
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And then I showed him this weird data that our citizen scientists had found,
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and he said to me,
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"Aw crap, Tabby.
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Now I have to rewrite my paper."
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So yes, the natural explanations were weak,
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and we were curious now.
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So we had to find a way to rule out aliens.
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So together, we convinced a colleague of ours
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who works on SETI, the Search for Extraterrestrial Intelligence,
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that this would be an extraordinary target to pursue.
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We wrote a proposal to observe the star
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with the world's largest radio telescope at the Green Bank Observatory.
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A couple months later,
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news of this proposal got leaked to the press
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and now there are thousands of articles,
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over 10,000 articles, on this star alone.
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And if you search Google Images,
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this is what you'll find.
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Now, you may be wondering, OK, Tabby, well,
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how do aliens actually explain this light curve?
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OK, well, imagine a civilization that's much more advanced than our own.
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In this hypothetical circumstance,
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this civilization would have exhausted the energy supply of their home planet,
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so where could they get more energy?
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Well, they have a host star just like we have a sun,
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and so if they were able to capture more energy from this star,
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then that would solve their energy needs.
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So they would go and build huge structures.
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These giant megastructures,
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like ginormous solar panels, are called Dyson spheres.
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This image above
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are lots of artists' impressions of Dyson spheres.
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It's really hard to provide perspective on the vastness of these things,
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but you can think of it this way.
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The Earth-Moon distance is a quarter of a million miles.
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The simplest element on one of these structures
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is 100 times that size.
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They're enormous.
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And now imagine one of these structures in motion around a star.
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You can see how it would produce anomalies in the data
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such as uneven, unnatural looking dips.
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But it remains that even alien megastructures
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cannot defy the laws of physics.
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You see, anything that uses a lot of energy
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is going to produce heat,
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and we don't observe this.
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But it could be something as simple
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as they're just reradiating it away in another direction,
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just not at Earth.
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Another idea that's one of my personal favorites
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is that we had just witnessed an interplanetary space battle
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and the catastrophic destruction of a planet.
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Now, I admit that this would produce a lot of dust
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that we don't observe.
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But if we're already invoking aliens in this explanation,
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then who is to say they didn't efficiently clean up all this mess
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for recycling purposes?
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(Laughter)
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You can see how this quickly captures your imagination.
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Well, there you have it.
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We're in a situation that could unfold
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to be a natural phenomenon we don't understand
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or an alien technology we don't understand.
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Personally, as a scientist, my money is on the natural explanation.
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But don't get me wrong, I do think it would be awesome to find aliens.
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Either way, there is something new and really interesting to discover.
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So what happens next?
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We need to continue to observe this star
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to learn more about what's happening.
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But professional astronomers, like me,
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we have limited resources for this kind of thing,
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and Kepler is on to a different mission.
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And I'm happy to say that once again,
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citizen scientists have come in and saved the day.
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You see, this time,
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amateur astronomers with their backyard telescopes
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stepped up immediately and started observing this star nightly
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at their own facilities,
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and I am so excited to see what they find.
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What's amazing to me is that this star would have never been found by computers
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because we just weren't looking for something like this.
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And what's more exciting
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is that there's more data to come.
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There are new missions that are coming up
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that are observing millions more stars
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all over the sky.
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And just think: What will it mean when we find another star like this?
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And what will it mean if we don't find another star like this?
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Thank you.
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(Applause)
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