Although there’s a lot of circumstantial evidence, we are yet to discover the crucial clue to prove the existence of a large ninth planet in the Solar System. And now researchers want the help of citizen scientists to discover if Planet 9 is real or not.

The project, called Backyard Worlds: Planet 9, lets people look at four-frame "flipbook" videos made out of images captured by NASA’s Wide-field Infrared Survey Explorer (WISE) observatory. If an object appears to be moving, it is probably very close and could be a nearby brown dwarf or the mysterious Planet 9.

“Backyard Worlds: Planet 9 has the potential to unlock once-in-a-century discoveries, and it’s exciting to think they could be spotted first by a citizen scientist,” UC Berkeley postdoctoral researcher Aaron Meisner said in a statement.

Meisner is a a physicist who specializes in analyzing WISE images and has been working on automating the search, as WISE covers the whole sky six times over. A single researcher can’t take on such a task and even machines have their limitations.

“Automated searches don’t work well in some regions of the sky, like the plane of the Milky Way galaxy, because there are too many stars, which confuses the search algorithm,” he continued.

He was able to automatically look at 5 percent of the WISE catalog, but he wasn’t able to find any new objects. Citizen scientists don’t have the limitation of computer programs and they are naturally more apt to see the tiny differences that might hint at an undiscovered object.

Meisner was approached by NASA astronomer Marc Kuchner to open the survey to the public, and the project was made available on the citizen science platform Zooniverse, which has hundreds of thousands of volunteers.

Each website user will be asked to look at four photograms from a region of the sky and then tasked with highlighting any object that might appear to be moving.

^{WISE video that highlights interesting objects. NASA/UC Berkeley/Zooniverse} 

Studying moving objects is the same technique that was used to discover Pluto in 1930. But unlike Pluto or the other planets in the Solar System, these objects are too far away from the Sun to be spotted using reflected visible light.

“There are just over four light-years between Neptune, the farthest known planet in our solar system, and Proxima Centauri, the nearest star, and much of this vast territory is unexplored,” said Kuchner. “Because there’s so little sunlight, even large objects in that region barely shine in visible light.”

And this is where WISE comes in. The objects, likely brown dwarfs but maybe Planet 9, glow in infrared, which means the NASA observatory can catch their light.

“We’ve pre-processed the WISE data we’re presenting to citizen scientists in such a way that even the faintest moving objects can be detected, giving us an advantage over all previous searches,” Meisner stated.

Planet 9 was first proposed at the beginning of 2016 to explain the curious orbits of many trans-Neptunian objects. Its alleged orbit lies at least 200 times farther than the Earth from the Sun, and while there’s a lot of enthusiasm for this potential new planet, until we see it, it remains a hypothesis.