Get to Know Your Neighbors (and Maybe Find Planet Nine in Your Spare Time!)

Instead of binge-watching one more episode of Game of Thrones or The Big Bang Theory, consider taking a few minutes to look at your cosmic neighborhood. You could be the one to discover a neighbor that has never been seen before—such as the alluring, hypothetical Planet Nine.

You don’t need an astronomy background or clear skies to join the search, just a computer, internet connection, and a bit of time. Already more than 16,000 citizen scientists are participating in Backyard Worlds: Planet Nine, which debuted just last week.

Astronomers hope that with the help of the public, they can quickly sift through a huge collection of images of the deep solar system, the area beyond Neptune. They hope to zero in on signs of Planet Nine and planet-like stars called brown dwarfs living at the edges of the solar system. Computers are experts at processing and sorting data, but even in 2017 there are some cases, like this one, in which human eyes are just better.

The data comes from NASA’s Wide-field Infrared Survey Explorer (WISE) mission, which surveyed the sky in infrared light during 2010 and 2011. The mission was reactivated in 2013 to look for potentially dangerous near-Earth objects like asteroids and comets.

Some models of Planet Nine suggest that it could give off infrared light that would be visible in WISE data. The problem is that we don’t know where Planet Nine is, what it looks like, or even if it exists. In addition, there is evidence that a group of undetected brown dwarf stars may be floating around in this region of the sky. Often called failed stars, brown dwarf stars are bigger than planets, but don’t get massive enough to fuse hydrogen into helium—the process that keeps regular stars burning. This makes them hard to find. However, brown dwarfs do give off some infrared light that could be visible in WISE data.

The best way to search for Planet Nine and brown dwarfs in WISE data is by looking at how objects move over time. As a kid, you may have created or played with flip books, small books with a slightly different image on each page. When you flip the pages quickly, the small variations between pages show up as movement. Essentially, Backyard Worlds is just a bunch of flip books. Each book includes four or more images from the same area of the sky, taken at different times (often separated by years). Objects that are closer to us, like brown dwarfs and Planet Nine, will appear to move faster across the sky than the distant stars and galaxies that make up the background in these images.

This sounds easy enough for a computer to handle, but in reality human eyes are significantly better. Computers can get distracted by especially bright stars or blurry bright spots resulting from issues with the WISE equipment. Humans, on the other hand, are more drawn to motion and can tune out these distractions more easily.

If you participate in Backyard Worlds, you’ll view these “flip books” as short videos. You can study each one as long as you want, watching for spots of light that appear to move differently than all of others spots. If you find one of these “movers,” you flag it, post a comment noting where you found it, and then search to see if it has already been catalogued. Given what astronomers already know is in that region of the sky from WISE and other sky surveys, you can expect about 1 mover per 60 videos. But it’s the potential for objects that astronomers don’t already know about that make this opportunity so exciting! If you find a mover hasn’t been catalogued yet, there is a special form to complete that alerts the project scientists to take a closer look.


Backyard Worlds is hosted on Zooniverse, a platform for research projects that use volunteers to help sort through data. If you need a break from searching for Planet Nine, you can help LIGO scientists search for gravitational waves with Gravity Spy, classify distant galaxies with Galaxy Zoo, look for exoplanets with Planet Hunters, or branch into fields ranging from literature to biology. These projects aren’t just about engaging the public, they are real research efforts and many have resulted in peer reviewed publications. Backyard Worlds is a collaboration that includes scientists from NASA Goddard Space Flight Center, University of California, Berkeley, Arizona State University, the American Museum of Natural History, and the Space Telescope Science Institute.

What are you waiting for? Go here to start searching!