Because of the limitations of telescopes, little more was learned of Pluto until the 70s. Pluto is about three billion miles from the sun and takes 248 years to complete its orbit. The orbit is eccentric, and at the moment it is closer to the sun than Neptune. In 1978 a satellite was discovered and named Charon. A robotic reconnaissance mission to the planet is planned by NASA for the first years of the next millennium.
Controversies continue to dog the planet.
Pluto s small size is thought to be too little to account for Lowell s perturbative observations, so it is suspected that another planet may lie at the solar system s fringes. Some astronomers doubt that Pluto is a planet at all, preferring to regard it as a part of a vast belt of cometoids hypothesized to surround the solar system. Tombaugh regarded such speculation as a bunch of nonsense. Clyde Tombaugh died January 12, nearly 66 years to the day from his discovery.