Evidence Found of Massive Planet 9 [Video]

Scientists have found evidence there’s a giant planet at the edge of our solar system. They’re calling it “Planet Nine.”

“This would be a real ninth planet,” says Mike Brown, professor of planetary astronomy at the California Institute of Technology. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting.”

While astronomers haven’t observed it directly yet, models suggests it has a mass about 10 times that of Earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average distance of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun.


The putative ninth planet—at 5,000 times the mass of Pluto—is sufficiently large that there should be no debate about whether it is a true planet. Unlike the class of smaller objects now known as dwarf planets, Planet Nine gravitationally dominates its neighborhood of the solar system. In fact, it dominates a region larger than any of the other known planets—a fact that makes it “the most planet-y of the planets in the whole solar system.”

The fascinating video on the next page tells the story of this “crazy” discovery, and how the researchers had to convince themselves that Planet 9 is really out there.