Astronomers have found — way beyond the orbit of Pluto — an intriguing distant object orbiting the sun.
It's just a dwarf planet, about 200 miles across, but some researchers think finding it increases the likelihood that there is a heretofore undiscovered giant planet lurking in the outer reaches of our solar system. That would bring the number of true planets in our solar system back to nine, replacing Pluto which was demoted in 2006.
Scott Sheppard and his colleagues at the Carnegie Institution for Science first spotted the new object, known officially as 2015 TG 387, around Halloween three years ago, so they gave it the nickname "The Goblin."
"It's on the small end of a dwarf planet," Sheppard says. "We don't know exactly how big it is, but we think it's about 300 kilometers in size, which is about six or seven times smaller than Pluto."
At first, all they knew about The Goblin was its distance from the sun: 7.5 billion miles. Astronomers can tell the distance of an object by how fast it moves across the sky. Objects close to the sun move rapidly, objects farther away more slowly. The speed gives the distance.