The solar system appears to have a new ninth planet.
Two scientists announced evidence that an unseen body nearly the size of Neptune orbits the sun every 15,000 years. During the solar system’s infancy 4.5 billion years ago, the giant planet was knocked out of the planet-forming region near the sun. Slowed down by gas, the planet settled into a distant elliptical orbit, where it still lurks today.
The claim is the strongest yet in the centuries-long search for a “Planet X” beyond Neptune.