In the 20th century, Pluto was discovered. After initial observations led to the belief that it was larger than Earth, the object was immediately accepted as the ninth planet. Further monitoring found the body was actually much smaller: in 1936, Ray Lyttleton suggested that Pluto may be an escaped satellite of Neptune, and Fred Whipple suggested in 1964 that Pluto may be a comet. As it was still larger than all known asteroids and the population of dwarf planets & other trans-Neptunian objects was not well observed, it kept its status until 2006.