Astronomers say a Neptune-sized planet lurks beyond Pluto
- The solar system appears to have a new ninth planet. Today, two scientists announced evidence that a body nearly the size of Neptune but as yet unseen orbits the sun every 15,000 years. During the solar systemâ€™s infancy 4.5 billion years ago, they say, 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.