Heroes of Space: Clyde Tombaugh

The amateur astronomer who discovered Pluto and visited the dwarf planet after his death

Clyde Tombaugh discovered dwarf planet Pluto in 1930. Image Credit: NASA

Clyde Tombaugh discovered dwarf planet Pluto in 1930. Image Credit: NASA

The existence of a planet beyond Neptune had been predicted by prominent American astronomer, Percival Lowell in 1905 but it was never proven in his lifetime. He had aimed a 40-inch reflector telescope at what he believed to be the right section of the sky, but he died in 1916 with his dream of discovering his so-called Planet X sadly unrealised. It was to be his biggest disappointment, yet it was the catalyst for a continued search. And, for amateur astronomer Clyde Tombaugh, Lowell’s hunch would yield great results.

Lowell’s legacy was the observatory that bore his name and which had been built in 1894 for the purpose of studying Mars. It had come to be looked after by his nephew, Roger Lowell Putnam, who in a twist of fate had been approached by Tombaugh in 1929, seeking feedback on his detailed drawings of Jupiter and Mars. Tombaugh was in his early 20s and he had built his own telescope. With an instant offer of a job, Tombaugh could never have foreseen what his decision to contact astronomers at the Lowell Observatory would lead to.

Tombaugh, who was born in Streator, Illinois and grew up on a farm in Kansas, was tasked with leading the search for Planet X using a device called a blink comparator – a piece of viewing apparatus used to discover the differences between two images of the night sky. By looking for apparent changes in the position of objects, Tombaugh struck upon something extraordinary after ten months of hard work. He noticed a planet-like body on 18 February 1930 and some three weeks later – on 13 March 1930 – Pluto’s discovery was announced.

It would prove to be an amazing start to Tombaugh’s career but it was not quite a case of him peaking early. Tombaugh continued to work at the Lowell Observatory until 1945 and he took the opportunity from 1932 to 1938 to study for a bachelor’s and master’s degree in astronomy at the University of Kansas. He was making a long-lasting contribution to the understanding and exploration of space and his discoveries would have ramifications for decades to come.

Clyde Tombaugh's ashes are on board the New Horizons spacecraft, which passed Pluto in July 2015. Image Credit: NASA

Clyde Tombaugh’s ashes are on board the New Horizons spacecraft, which passed Pluto in July 2015. Image Credit: NASA

Certainly, his qualifications stood him in good stead during his time teaching astronomy at New Mexico State University from 1955 until his retirement in 1973, but it was his other discoveries that provided the icing on the cake. He found hundreds of new variable stars and asteroids and also discovered two comets and thousands of new star and galaxy clusters. Fittingly, Asteroid 1604 Tombaugh, which he discovered in 1931, was named after him. And, some others were named after his family.

Indeed, Tombaugh was a family man and when he died on 17 January 1997 at the age of 90, he left behind his wife, Patricia, and his two children, Annette and Alden. Whether fortunate or not, this meant he wasn’t around in 2006 when the International Astronomical Union voted to re-classify Pluto as a dwarf planet, following the 2003 discovery of Eris and the observation of other smaller sized bodies in the Kuiper Belt – the circumstellar disc which extends beyond the orbit of Neptune. Quite what he would make of the controversial downsizing of his iconic discovery will therefore never be known, but Tombaugh’s story does not stop there.

In that same year, New Horizons was launched from Cape Canaveral to study the Pluto system and, as a secondary mission, the Kuiper belt. On the inside of the upper deck of the probe was affixed a small container carrying Tombaugh’s ashes.

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