Seventy-five years ago a young amateur astronomer made the find of a lifetime when he discovered Pluto, the ninth planet. Clyde Tombaugh became famous for his discovery on 18 February 1930, and rightfully so. But in recent years there has been an effort to remove Pluto's planetary status and label it as a comet.

Whatever its status as a planet, the discovery of Pluto was no accident. In his search for what was then called Planet X, the 26-year old Tombaugh spent endless hours staring at alternating photographic negatives. Any object that changed positions from one plate to the next would have to be something other than a star. When Tombaugh found a tiny object that changed places on two successive images, he knew he had found the elusive Planet X.

Tombaugh died in 1997, and amateur astronomers continue to make significant discoveries. In 2003 the Society for Amateur Scientists awarded its Benjamin Franklin Citizen Scientist Award to David Levy for his co-discovery of the Comet Shoemaker-Levy, the string of 21 comets that crashed into Jupiter in 1993. The impact of the string of comets is the only time that a comet has been observed to strike a planet.

Forrest M. Mims III