Backyard Worlds: Planet 9 is an international scientific collaboration to search for undiscovered planets in our solar system, especially a super-Earth orbiting at the edge of the solar system. The project uses citizen science to comb through data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission. By looking for moving objects in this large dataset, anyone can help us find new worlds!
The discovery of “Planet Nine” was first proposed in 2016 by Caltech astronomers Konstantin Batygin and Michael Brown. They found evidence that something roughly 10 times the mass of Earth and 20 times farther from the sun than Neptune must be wobbling the orbital planes of a group of six known objects beyond Neptune. This putative ninth planet would explain the unique orbits of these bodies, which are clustered together in space and tilted away from the plane on which most planets orbit.
In 2018, a team led by Carnegie Institution for Science astronomer Scott Sheppard found more evidence supporting the existence of Planet Nine. Sheppard’s team used computer simulations to show that there could be thousands of small objects on similar orbits as those six known bodies–orbits that point to the existence of an unseen massive planet.
As WISE survey data became publicly available, citizen scientists started finding potential new candidates for Planet Nine using Backyard Worlds: Planet 9. So far, four professional astronomers have been alerted to potential new discoveries by participants in the project!