After many other suggestions and much debate, the planet was named Pluto partly due to its distance from the sun, which keeps it perpetually in the dark, and partly because "PL" are the initials of Percival Lowell, the man who theorized the existence of another planet and whose laboratory its discoverer, Clyde W. Tombaugh worked. Pluto is the most recent planet in the solar system to be detected (1930).
In 2005, a planet, larger than Pluto, was discovered using the Samuel Oschin Telescope at Palomar Observatory near San Diego, Calif. It has tentatively been called Xena while awaiting a decision by the International Astronomical Organization on its status and name. Catalogued as 2003UB313, it was first photographed with the 48-inch Samuel Oschin Telescope on October 31, 2003.