The Alien Seeker News Clyde Tombaugh, Ph.D. Biography American astronomer who discovered the planet Pluto. On August 20, 1949, he observed a UFO that appeared as a geometrically arranged group of six-to-eight rectangles of light, window-like in appearance and yellowish-green in color, which moved from northwest to southeast over Las Cruces, New Mexico. He stated: "I doubt that the phenomenon was any terrestrial reflection, because... nothing of the kind has ever appeared before or since... I was so unprepared for such a strange sight that I was really petrified with astonishment."