Today in Science History – January 17 – Pluto

Pluto New Horizons
Pluto as seen by New Horizons probe.

January 17 marks the passing of two people, William Pickering and Clyde Tombaugh, who was important to the discovery of the dwarf planet, Pluto.

William Pickering was an American astronomer known for opening new observatories and research stations. He also believed there should be a planet outside the orbit of Neptune. Neptune and Uranus’ orbits did not fit the orbit they should have if accounting for the masses and positions of all the known planets. Pickering established Lowell Observatory in Flagstaff, Arizona with Percival Lowell with the job of finding this “Planet X”. Powell would spend the rest of his life searching for Planet X but never found it.

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. He also discovered Lowell photographed the planet on two separate occasions but did not recognize it as what he was looking for.

Fun Trivia: 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. She thought the planet should be named for the Roman god of the underworld and mentioned it to her grandfather. He submitted her suggestion to Lowell Observatory.

Notable Science History Events for January 17

1997 – Clyde William Tombaugh died.

Clyde William Tombaugh
Clyde William Tombaugh (1906 – 1997).
Lowell Observatory Archives

Tombaugh was an American astronomer who discovered the dwarf planet, Pluto while searching for Percival Lowell and William Pickering’s Planet X that would explain the orbit of Neptune. He also discovered 14 asteroids. Tombaugh claimed he observed lights near Las Cruces, New Mexico he claimed were UFOs.

1946 – Clarence E. McClung died.

Clarence Erwin McClung
Clarence Erwin McClung (1870 – 1946)

McClung was an American biologist who discovered chromosomes determine the sex of a species. He also researched the effect of chromosomes had on heredity. He was researching the chromosomes in insects when he found the accessory chromosome was present in every cell until the organism is fully formed and then it is present in one-half of the gametes of the sex that carries it. Since this chromosome divides organisms into two groups and sex divides organisms into two groups, perhaps one had something to do with the other.

1938 – William Henry Pickering died.

William Henry Pickering
William Henry Pickering (1858 – 1938).
Library of Congress

Pickering was an American astronomer who discovered Phoebe, the ninth moon of Saturn. He believed he had discovered a tenth moon and named it Themis, but his moon turned out to be artifacts on the photographic plates. He also searched for “Planet X”, a planet that he predicted to be outside the orbit of Neptune that caused perturbations in the orbits of Uranus and Neptune.

1911 – Francis Galton died.

Francis Galton
Francis Galton (1822 – 1911)

Galton was an English polymath who is best known for his early work in eugenics or the selection of parents to increase beneficial traits into their offspring. He also proposed the use of fingerprints as a unique identifier of individuals and developed the classification system still in use today.

1910 – Friedrich Wilhelm Georg Kohlrausch died.

Friedrich Kolrausch
Friedrich Kolrausch (1840-1910)

Kohlrausch was a German physical chemist who focused on the thermal, electrical and magnetic properties of electrolytes. Electrolytes are substances that conduct electricity in solutions through the transfer of ions. He was the first to demonstrate electrolytes have a constant electrical resistance and measured the velocities of the transferred ions for a particular electrolyte.

Read more about Kohlrausch on October 14 in Science History.