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Citizen scientists have discovered a brown dwarf 100 light-years from the Sun, and more finds are sure to come from the Backyard Worlds citizen-science project.

Believe it or not, there are exotic celestial objects hiding closer than we think — just a short distance from the Sun. And we want to find them. That’s why, last February, I helped launch Backyard Worlds. The citizen-science project invites anyone in the world to join the search for new worlds close to our own Sun. We’ve already found one — a brown dwarf just 100 light-years away.

To get started in Backyard Worlds, all you need is access to a computer and an Internet connection. We ask users to create a username that links to your email so if you do end up finding something interesting; we know how to give you proper credit. Once you’re logged in, the exploration begins: you begin flipping through images taken by a NASA spacecraft called WISE, the Wide Field Infrared Survey Explorer, and scan for objects that appear to move over time.

All celestial bodies in our galaxy are moving. A planet orbits its parent star, which in turn can be found moving with other stars in an association, and all of those are moving around the galaxy. Stars, planets, comets, and other objects all move at different speeds. If an object is close enough, you can look at two images taken a few years apart, flip between them, and catch the object "jumping" relative to the background stars. Within the Backyard Worlds, more than 39,000 volunteers have been examining more than 4 million such "flipbooks" of the sky .

Six days after the project launched, a user alerted our science team to one such object that appeared to be nearby and cold — in other words, not a star. In all, four citizen scientists alerted our team to the source: a science teacher in Tasmania initially reported the faint object, and volunteers from Russia, Serbia, and Sweden tagged it as well. After some excitement and investigation, we decided that this was the kind of object that we wanted to follow up: Its fast motion in the flipbooks was exciting, but to truly understand the nature of the source we needed to obtain a spectrum.

Typically, telescope time requires several months of lead time and an evaluation by a time allocation committee, but under these special circumstances, we were able to request a small window of discretionary time on NASA's Infrared Telescope Facility. After a few hours of observing the target, its nature became clear. This was a brown dwarf, just a few hundred degrees warmer than Jupiter, that had previously been hidden from sight. It lies only 100 light-years away, but it’s so faint, previous surveys had missed it in their searches of the sky.

Brown dwarfs are abundant in the Milky Way, though their dimness makes them hard to find. They lack the mass to keep hydrogen burning, but they’re hot enough to glow faintly at infrared wavelengths. They’re also strikingly similar to Jupiter, so we study their atmospheres in order to understand what weather on other worlds might look like.

While the Backyard Worlds project is ultimately hoping to find the infamous Planet 9 hiding in our own solar system, these new brown dwarfs are also exciting discoveries. It's possible that one of these cold worlds might lie even closer to us than Proxima Centauri, the star nearest the Sun. If it does, one of our citizen scientists is going to find it.

So far, volunteers have given our research team several great targets for telescopic follow-up. Given enough time, I think our volunteers are going to map out our whole solar neighborhood. Anyone can participate and join the search party at backyardworlds.org.

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