January 17th marks the passing of two people, William Pickering and Clyde Tombaugh, who were important to the discovery of the dwarf planet, Pluto.
William Pickering was an American astronomer who believed there was a planet outside the orbit of Neptune that caused the unusual shape of the orbit of Neptune and Uranus. He was instrumental in the establishment of Lowell observatory in Flagstaff, Arizona with Percival Lowell to search for this "Planet X". Powell spent the rest of his life searching, even photographing Pluto on film twice without recognizing the planet.
Clyde Tombaugh joined the staff at Lowell Observatory and was given the task of taking systematic photographs of portions of the night sky on two nights one week apart. He would load the images in a device called a blink comparator that rapidly switches the two photographs. This allowed Tombaugh to detect slight differences between the photographs which would suggest movement. He found a change from his late January plates and confirmed the discovery with another photograph. He had discovered a new planet and the formal announcement was made on March 13, 1930.
The name "Pluto" was chosen from a selection of submitted possible names. It originally came from an 11-year-old girl from Oxford, England named Venetia Burney. Find out what else occurred on this day in science history.
William Pickering was an American astronomer who believed there was a planet outside the orbit of Neptune that caused the unusual shape of the orbit of Neptune and Uranus. He was instrumental in the establishment of Lowell observatory in Flagstaff, Arizona with Percival Lowell to search for this "Planet X". Powell spent the rest of his life searching, even photographing Pluto on film twice without recognizing the planet.
Clyde Tombaugh joined the staff at Lowell Observatory and was given the task of taking systematic photographs of portions of the night sky on two nights one week apart. He would load the images in a device called a blink comparator that rapidly switches the two photographs. This allowed Tombaugh to detect slight differences between the photographs which would suggest movement. He found a change from his late January plates and confirmed the discovery with another photograph. He had discovered a new planet and the formal announcement was made on March 13, 1930.
The name "Pluto" was chosen from a selection of submitted possible names. It originally came from an 11-year-old girl from Oxford, England named Venetia Burney. Find out what else occurred on this day in science history.

Comments
One minor correction: The name is William Pickering, not Pinkering. Also, many scientists continue to view Pluto as a planet. Only four percent of the International Astronomical Union voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed in a formal petition of hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto, which launched four years ago today on January 19, 2006 and will arrive at Pluto in 2015.
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