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Aliens are not a thing. We know this, right? Well, maybe. Turns out that, almost despite themselves, some of the world’s leading astronomers are taking seriously the question of whether or not we are alone on Earth. Among them, Yale’s Tabetha Boyajian, who has stumbled into what might be one of the biggest mysteries in the galaxy.

It centers on a star known as KIC 8462852, tucked in the constellation Cygnus, more than 1,500 light years away from Earth. In 2015, using data from NASA’s Kepler space observatory, citizen scientists from Planet Hunters noticed something weird: something roughly 1,000 times the area of Earth was blocking the light from the star. This transit, as such dimming is known, was also happening in an unusual, unpredictable pattern. Some say massive clouds of star-making material might be blocking the light, while others think swarms of giant comets are getting in the way. But there’s another possible explanation that has yet to be ruled out: giant, alien-built megastructures. In this Q&A, Boyajian shares more details on KIC 8462852, now affectionately known as Tabby’s Star (a name she claims no responsibility for coining), and herein shortened to KIC 846 (a name she’s cool with).

How could the existence of an alien civilization explain the dimming of the light coming from KIC 846?

Imagine a civilization that’s much more advanced than our own. After it exhausted the energy supply of its home planet, that civilization builds giant structures to orbit its star and capture more of its energy. These structures, known as Dyson spheres after the physicist Freeman Dyson (TED Talk: Let’s look for life in the outer solar system), would be ginormously huge. It’s really hard to provide perspective on the vastness of these things. Think of it this way: the distance from the Earth to the Moon is a quarter of a million miles. The simplest element on one of these structures is 100 times that size.

Now imagine one of these structures in motion around the star, and you can see how it would produce anomalies in the data, such as uneven, unnatural-looking dips in that star’s brightness.

How likely is it that we are seeing evidence of Dyson spheres around KIC 846?

Until we have data to rule it out, intelligent life remains a possibility. However, it’s highly improbable that this is the answer, and it goes under a list of bad hypotheses that we have to explain the star’s observations. I’d give it a one-in-a-million shot.

But you haven’t ruled it out, and you co-authored a proposal to have the SETI Institute (Search for Extraterrestrial Intelligence) take a closer look at the star. Did you have doubts before putting forward a hypothesis involving Dyson spheres in a serious way?

I thought really long and hard whether or not this was the right thing to do, because if you are seen to give up on physics and to start exploring the unnatural, people stop taking you seriously. That’s scary for a scientist, especially for me because I’m very young in my career.

But this is an exceptional case of a truly unique and poorly understood system, and in the end I was curious. So if exploring unnatural causes could rule out yet another scenario to explain the star’s unusual observations, I believe this motivation has value, even if it’s breaking the traditional mold of how science is done. Overall, I’ve been impressed by the support from my colleagues on this, as I think we can all learn something in the end. That is what science is about, after all — exploring new things.

There are a lot of astronomers who are really excited about the possibility that we might one day discover that we’re not alone, that there’s something else out there. At the same time, a conservative scientific culture demands hard evidence for this kind of extraordinary stuff. How do you straddle the line between the two?

This is a complicated situation. There are scientists who devote their whole life to searching for life beyond earth. SETI is a whole field of study, like biology or chemistry. But here’s the catch: even though astrophysics and SETI both study the cosmos, the science doesn’t mix much. We don’t cite each other’s papers. For an astronomer to even consider that traditional observations could be explained by something unnatural can easily be seen as being reckless.

We haven’t given up on the fact that the unusual dimming pattern coming from KIC 846 is likely caused by a natural phenomenon we don’t understand. We’re just broadening the list of prospective scenarios. At this point, we haven’t been able to rule out aliens, but we haven’t been able to confirm any natural theories either. We need more data to say anything for sure.

With this in mind, it’s possible that this binary nature is due to scientists being extra cautionary on how they present results to the public. If something extraordinary such as life beyond Earth is detected, then we’d better be prepared to unequivocally back up such a statement. In this case, astronomers crossed this imaginary line and wrote a SETI proposal, but that’s far from a result.

How is KIC 846 currently being studied?

Right now, the star is just becoming visible again. Most celestial objects are only seasonally visible from Earth at night, and observing this star at night is not possible during the months of December through March.

We are currently working on initiating observing campaigns to monitor the star so we can catch it in action again. When this happens, we will be able to learn more about what’s orbiting the star and blocking the light. We have to learn more about this star, because it’s a huge mystery. It’d be crazy not to.

What do we need to confirm — or rule out — extraterrestrial activity on or around KIC 846?

Disclaimer: I am an astrophysicist and not an expert on SETI research.

A robust natural explanation that works to explain the star will take precedence over extraterrestrial activity, as the simplest explanation is likely the correct one. New data on this star will be taken at several different wavelengths, or colors, of light. When the star is seen to drop in brightness again, we should be able to distinguish between a natural body, like a dust cloud, or an artificial structure fairly easily by how the dips look in these different colors.

On the other hand, if some kind of seemingly unnatural activity is detected, such as beacons or leaked communication, it would still require verification along with exhaustive hypothesis testing that extraterrestrial activity is the cause.

For argument’s sake, let’s imagine that tomorrow SETI announces that it has found evidence of technology-related radio signals coming from KIC 846. What do we do next? How would that change how we view our place in the universe?

This is a question for each and every one of you to ask yourself.

Citizen scientists on Planet Hunters discovered KIC 846. Do you think this discovery will change how professional astronomers shape some future missions?

There are new missions starting very soon that will deliver data similar to Kepler, for many, many more stars all over the sky. Kepler looked at a fixed piece of the sky about as big as your fist when held at arm’s length. This is a tiny fraction, amounting to only a couple tenths of a percent, of the whole sky. By observing more of the sky in the way Kepler did, we hope to find many more stars with irregular or interesting transit patterns.

We would never have found this star, or anything like it, with computers or algorithms alone. The discovery of this star definitely motivates searching for other stars like it, whether it’s through crowdsourcing or possibly through machine learning in the future. But nature is very creative, and it’s fair to say that searching for the unexpected will remain an exciting and challenging area of science.