Citizen-science Project Invites Public to Search for New Nearby Worlds

An illustration of a purple planet-like object in a dark star field
This artist's concept illustrates a close-up view of a cool brown dwarf. Objects like this, drifting just beyond our solar system, have been imaged by NASA’s Wide-field Infrared Survey Explorer and could be discovered by Backyard Worlds: Planet 9.

A new citizen-science tool released today will help astronomers search for new worlds lurking in the outer reaches of our solar system and in neighboring interstellar space. Backyard Worlds: Planet 9 is making available to the public brief “movies” made from images captured by NASA's Wide-field Infrared Survey Explorer (WISE) mission and encouraging viewers to flag objects that appear to be moving for investigation by scientists. The tool was developed by scientists at NASA, Arizona State University, the University of California Berkeley, the Space Telescope Science Institute in Baltimore, the science crowdsourcing site Zooniverse, and the American Museum of Natural History.

Animated gif that flips through 4 images of patches of night sky.
A video composed of multiple still images from one patch of sky taken since 2016.
Courtesy of NASA


“It’s hard to believe, but our solar neighborhood is still unexplored territory,” said Jackie Faherty, a senior scientist in the Museum’s Department of Astrophysics and a collaborator on the project. “There are cold worlds hiding just a short distance from the Sun, and Backyard Worlds: Planet 9 is a platform for bringing citizen scientists into the search party .”

Unlike more distant sources, objects near our solar system appear to move across the sky, so the best way to discover them is through a systematic search of moving objects in WISE images. While parts of this search can be done by computers, machines are often overwhelmed by image artifacts, especially in crowded parts of the sky. This visual “noise” includes spikes associated with star images and blurs caused by light scattered inside WISE's instruments.

Human eyes, on the other hand, easily recognize important moving objects while ignoring other artifacts. By harnessing the eyes of viewers around the world, Backyard

Worlds: Planet 9 offers a 21st-century, scaled-up version of the technique astronomer Clyde Tombaugh used to identify Pluto in 1930, a discovery that was made 87 years ago this week.

On the Backyard Worlds: Planet 9 website, participants from around the world can view millions of "flipbooks," brief animations showing how small patches of the sky changed over several years. Moving objects flagged in these animations will be prioritized by the science team for follow-up observations by professional astronomers. Sharp-eyed participants will share credit for their discoveries in any scientific publications that result from the project.

WISE has scanned the entire sky several times since 2010, snapping pictures of three- quarters of a billion objects, including remote galaxies, stars, and asteroids. The new project uses all of this data to search for unknown objects in and beyond our own solar system and takes part of its name from Planet 9, the nickname for a predicted but undiscovered world that may exist in the outer solar system—also known as Planet X. Last year, astronomers at the California Institute of Technology showed that several distant solar system objects possessed orbital features indicating they were affected by the gravity of an unseen planet far beyond Neptune. If Planet 9 exists and is as bright as some predict, it could show up in WISE data.

The search also may discover more distant objects like brown dwarfs, sometimes called failed stars, in nearby interstellar space.