Its discovery began with Sedna.

Sedna is a dwarf planet smaller than Pluto.

Scientists believe Sedna is in the gravitational pull of a large object, which could be this new planet — aka "Planet 9." (Video via Kurdistan Planetarium)

It has about 10 times the mass of Earth.

It's an average of 600 times farther from the sun than the Earth is and takes 20,000 years to orbit the sun once.

This video includes images from NASA.

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Martin Luther King Jr. Day and Juneteenth, among others, will no longer be considered fee-free days at U.S. National Parks. While the MLK National Historic Park in Atlanta doesn't charge admission, the new schedule will affect such metro Atlanta sites as Kennesaw Mountain National Battlefield Park. (Miguel Martinez/AJC)

Credit: Miguel Martinez-Jimenez

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Former Fulton County election worker Ruby Freeman talks to her daughter, Wandrea ArShaye "Shaye" Moss, a former Georgia election worker, after she testified before the U.S. House Select Committee at its fourth hearing on its Jan. 6 investigation on Capitol Hill in Washington, D.C., on Tuesday, June 21, 2022. (Yuri Gripas/Abaca Press/TNS)

Credit: TNS