It’s the stuff we’re used to seeing in movies—a mysterious large planet, sitting at the very fringes of our solar system. This time, it’s not the sci-fi spawn of Spielberg, but instead something very real. At a distance a thousand times farther from the Sun than Earth is, there waits an undiscovered world astronomers call “Planet Nine.” More than 175,000 volunteers have been combing NASA data to find this hypothetical planet. We know it as a cold world roughly around the size of Neptune. This planet theoretically lives far beyond the Kuiper belt within the solar system’s outermost region.
In 2016, California Institute of Technology astronomers Mike Brown and Konstantin Batygin found indirect evidence of an unseen ninth planet’s existence after uncovering its gravitational effects on the most distant objects known in the solar system. Some have alternatively theorized that the object is a black hole with the same mass of a planet.
For the last three years, hundreds of thousands of “citizen scientists” have sought further proof of the elusive cold world. Backyard Worlds: Planet 9 comprises a network of volunteers spread across the globe, working together on a NASA-funded project that lets pretty much anyone join a mission to find mysterious objects in spacecraft data. That’s right—you don’t need a Ph.D in physics to participate in the hunt for Planet Nine.
Backyard Worlds: Planet 9 was founded in 2017 through a collaboration between NASA, UC Berkeley, the American Museum of Natural History in New York, Arizona State University, the Space Telescope Science Institute, and people-powered research platform Zooniverse. The organization uses images captured by NASA’s Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission, giving the public digital access to millions of “flipbooks.” These brief animations show how small patches of the sky changed over several years; this data allows participants to flag any moving objects. Astronomers involved in the project then examine these findings.
Citizen scientists reviewing the satellite data aren’t trying to stumble upon just one elusive planet. They search for all types of undiscovered worlds. For instance, brown dwarfs, otherwise known as failed stars. They’ve found quite a few of those, too. A running count on the website shows nearly 1.5 million classifications and over 218,000 completed subjects as the latest project statistics.
In August, astronomers published a study reporting 95 new brown dwarfs discovered in space, with contribution from Backyard Worlds’ findings. NASA shared that the citizen science network has helped find over 1,500 cold worlds in the last three years. The space agency called this “the largest published sample of these objects ever discovered through a citizen science project.” Early in 2019, a volunteer discovered what scientists believe could be the oldest and coldest white dwarf with multiple dust rings.
A lead author of those studies is Aaron Meisner, who also co-founded Backyard Worlds: Planet 9. Meisner says that as of October, more than 175,000 overall participants are behind the project’s achievements; nearly 63,000 have registered on the online database. A Harvard and Stanford grad, Meisner is an assistant scientist at the National Science Foundation’s NOIRLab and a 2018 NASA Hubble Fellow. His work focuses on using processing data from modern supercomputers to map the universe in new ways.
“There’s this concept of looking for things that move in the sky, as a way of finding things that are very nearby to us. And that’s one of the oldest techniques in astronomy,” Meisner told
Meisner continued, “And so myself and some of my colleagues thought: ‘Why don’t we just crowdsource this process and remove this bottleneck? And open up a new port of discovery that way?’” Meisner and his team realized that instead of having a few people look at hundreds of thousands of images, there was another approach. He said, “What if we just had tens of thousands of people each look at a much smaller number and still cover a huge amount of data?”
Thus, they formed a large, crowdsourced group of people, spreading out to cover new datasets and mining for discoveries. It’s the power of citizen science in action. They’re hard at work, but they haven’t found the ninth planet in our solar system…yet. If they do, the implications will be cosmic.
“I think it would change the way that we understand the formation and evolution of our own solar system and other solar systems out there in the galaxy,” Meisner said. “I would really like to discover Planet Nine, if it exists… And it would be an even better story if we could have it be discovered by a citizen scientist, sitting at home on their sofa.”