#Planet #Pluto – The Rise and Fall of Planet Pluto : Percival Lowell knew something else was out there. Based on his calculations, the American businessman and astronomer was convinced that an unknown ninth planet was responsible for the wobbling orbits of Uranus and Neptune.
For more than a decade until his death in 1916, Lowell peered into the shroud of darkness from the observatory he founded in Flagstaff, Arizona, but he never could find his elusive “Planet X” on the edge of the solar system.
Then in the winter of 1930, as 24-year-old observatory assistant Clyde Tombaugh tediously compared photographs of a section of the night sky, he noticed a tiny speck of light on his plates had moved against the fixed background of stars.
It was Planet X-right where Lowell calculated it would be. The Lowell Observatory announced its discovery of the ninth planet on March 13, 1930, the anniversary of its founder’s birth.
At the suggestion of 11-year-old English schoolgirl Venetia Burney, the new planet was christened Pluto after the Roman god of the underworld, beating out other suggested names such as Minerva and Erebus.
As astronomers learned more about Pluto, however, it turned out that the solar system’s outermost planet was a celestial oddball. It had the most elliptical and tilted orbit of any planet.
At the closest point on its 248-year transit of the sun, Pluto passed inside the orbit of the solar system’s eighth planet, Neptune. While at the time of discovery astronomers announced the distant planet “may be bigger than Jupiter,” Pluto turned out to be even smaller than Earth’s moon.
As more was learned about it, astronomers began to question whether Pluto had gained admission to the exclusive planetary club based on inflated credentials. Then in 1992, Massachusetts Institute of Technology scientists Jane Luu and David Jewitt discovered beyond Pluto’s orbit conclusive evidence of the Kuiper belt, a vast zone of debris left over from the formation of the solar system.
Among the hundreds of celestial bodies orbiting the sun in the Kuiper belt were those similar in size and mass to Pluto. When Caltech astronomers led by Mike Brown discovered Eris, which had a greater mass the Pluto, in the Kuiper belt in 2005, it became clear that a change needed to be made to the membership of the solar system’s planetary club.
When the International Astronomical Union (IAU) gathered in Prague in August 2006, the world’s top astronomical body considered a plan to expand the solar system to 12 planets with Pluto and its moon Charon, which is half its size, recognized as a twin planet.