Last week, two scientists announced evidence of a planet roughly the size of Neptune with a mass 10 times that of Earth's and a thick atmosphere of hydrogen and helium. The planet is so far away that its year would last 10,000 to 20,000 Earth-years.

The planet has not actually been seen yet, though. Rather, two planetary scientists, Konstantin Batygin and Mike Brown of the California Institute of Technology, theorized that it exists, DNews' Trace Dominguez and Amy Shira Teitel explained in the video below.

Interestingly enough, it was Mike Brown's discovery of the dwarf planet Eris that caused the International Astronomical Union to demote Pluto from a planet to a dwarf planet in 2006. So the researcher responsible for the formal change from nine to eight planets a decade ago is now saying there might actually be a ninth planet.

Batygin and Brown inferred so-called Planet X or Planet Nine's existence from an unusual cluster of six objects orbiting beyond Neptune in the Kuiper Belt. They argued that the only explanation for this unusual cluster is the gravitational pull of a massive planet.

"This might sound like a lot of sketchy guess work, but it's actually a viable method of finding planets that has worked before," Teitel said. It's the same way that astronomers discovered the existence of Neptune, Teitel explained. Once they had mathematical models showing where to look for Neptune, it wasn't long before they spotted the planet with a telescope.

However, finding this new planet may not be quite as easy, given how much further away from Earth it is than Neptune. "As researchers continue to refine their simulations, they'll learn more about Planet 9's orbit and influence on the distant solar system," Dominguez said.

"In the meantime," Teitel said, "astronomers are going to start sky hunting."

Watch the video from DNews here:


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