Calling Citizen Scientists: You Can Help Find Exoplanets From Your Couch

If you’ve ever wanted to help find an exoplanet, this is your chance. There’s a new open research initiative that invites participants to help identify exoplanets using simple visual pattern matching — and it’s open to anybody who wants to help. You don’t even have to own a telescope.

The project is an open, distributed search for exoplanets, in cooperation with a planet-hunting telescope array called the Next-Generation Transit Survey (NGTS). You can be a seasoned pro-am astronomer with a gigantic Dobsonian on your patio, or you might never have tried to engage in one of these projects before. It doesn’t matter your level of experience; you’re invited.

What they need is help identifying the dip in a star’s brightness when a planet transits in front of it. To do this, participants visually compare images to see whether there is a characteristic shape to the “light curve” of a star’s brightness over time. If the pattern is recognized, it’s tagged for further analysis.

The stars identified as having transiting planets are rare to begin with, because these planets’ orbits have to be precisely edge-on toward us. As a transiting planet swoops around between us and its star, the speed, shape, and eccentricity of the planet’s orbit all impact the rate at which it occludes the parent star’s light. In a sense, transits are like an eclipse, only the blip in a star’s brightness is much smaller because stars are so large.

So far, transit hunting is our most successful way of finding planets outside our solar system. You may remember that NGTS isn’t the only major array using the transit method. TESS also searches for transiting planets, much like Kepler.

Planets orbiting their stars should be as regular as clockwork — but there are things that can influence a star’s brightness as seen by our telescopes.

There’s also the problem of sunspots. Our sun has a whole sunspot cycle, with periods of increased and decreased sunspot activity. Because it oscillates between those two states, an observer at a high or low point in the cycle might not get a representative sample of our sun’s activity. We’ve seen this happen on other stars too. For example, the case of the asymmetrical dimming and subsequent brightening of Betelgeuse from October 2019 through February 2020. A mammoth gas expulsion that dimmed the star and disturbed a relatively large percentage of the star’s surface was determined to be the reason for the weird visuals we saw.

Our own atmosphere is another problem. Like other earthly telescopes, NGTS has to deal with the same atmosphere that makes stars twinkle to the naked eye. This is why the twelve telescopes that make up the NGTS array are installed at the ESO’s Paranal observatory. It sits in its aerie in the Chilean Andes, next to the Atacama desert. It’s so dry, and it lies at such an altitude, that it’s as close to space as you can get without actually putting the whole observatory in orbit.

The imaging frequency of NGTS is slower than TESS or Kepler. There’s also intermittent downtime. That’s important because participants are asked to decide two things: whether a given dip in a brightness curve is more like a U, a V, or a flat bottom, and whether a pattern of dips is regular enough to be an orbital transit. Fewer data points makes it tougher to get an accurate sense of a trend. If the image capture and the transit interval were timed just right, the camera could miss a transit every time. This is one place where machines just haven’t quite caught up with humans.

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