Nearly 3,500 exoplanets have been discovered to date, but in comparison, only 1281 brown dwarfs were found as of 2012—which is rather unexpected. For one thing, brown dwarfs are bigger and brighter than exoplanets, and so, you would think, easier to spot. Secondly, it seems intuitive that the models used to predict how many stars and planets should exist in our galaxy would also be able to estimate the number of brown dwarfs out there–but it isn’t quite so straightforward. Different detection methods limit how many of each type of object astronomers can find, and with a small sample of objects, the models can’t make precise population predictions.
Despite these challenges, astronomers do know with some certainty that there are likely many more brown dwarfs to be discovered. Within even 10 parsecs of the Sun (~33 light years or 191,700,000,000,000 miles), there could be as many as 60 super cool brown dwarfs known as Y dwarfs, floating through space on their own, waiting to be found. Y dwarfs are the size and temperature of gas giant exoplanets, like Jupiter, and are interesting to scientists because of their relatively close proximity which would provide close-up views into their atmospheres.
It isn’t easy to see these cold objects, even though they emit their own light and some of them are located nearby. To detect exoplanets, astronomers typically use the transit method—a method that involves looking for the shadows created by the planets as they pass in front of their host stars. Sometimes this method is used to find brown dwarfs since they, too, can orbit around larger stars. But most of the time brown dwarfs are free-floating in space. In this case, astronomers see them by spotting the light they emit, like stars, though their amount of light is much less significant. It’s a difficult task and one that requires tedious and lengthy image scrutinizing—so astronomers have once again turned to the public for help.
Screenshot of NASA’s “Backyard Worlds: Planet 9” Project on Zooniverse.org.
A new citizen science project offered through Zooniverse.org called “Backyard Worlds: Planet 9” provides participants with the tools they need to help astronomers hunt down these expected Y dwarfs. By examining a series of images, citizen scientists can locate moving targets, thus potentially discovering new, never-before-seen brown dwarfs located near our Sun. The images come from NASA’s Wide-field Infrared Survey Explorer (WISE) telescope and are laid out in time-order, so the viewer can spot an object if it’s moving, just like in a flip-book. If new brown dwarfs are discovered, the team will identify the best candidates for follow-up observations.
While the opportunity to discover a brown dwarf without leaving your home is exciting enough, there are even bigger prizes to be had—the possibility of discovering a whole new planet. Namely, the elusive “Planet Nine,” which astronomers predict is orbiting our Sun at an epic distance of nearly 111,550,000,000 miles away—at the very edge of our Solar System. But don’t be deterred—Planet 9’s orbit lies within the scope of the “Backyard Worlds: Planet 9” project, and may just be waiting for YOU to find it.
For more information and to learn how to participate, visit the project’s website.