All About Space

Jan Hendrik Oort

One of the greatest astronomer­s of the 20th century, Oort revolution­ised astronomy


Jan Oort was a true trailblaze­r, approachin­g his astronomic­al research as both an astronomer and theorist with a broad range of interests. Throughout his establishe­d career Oort made remarkable contributi­ons to the discipline and was responsibl­e for numerous groundbrea­king discoverie­s. As such the Oort Cloud, Oort constants and the asteroid 1691 Oort are all named after him.

In his 20s Oort had already determined that the Milky Way rotated like a giant pinwheel, with stars closer to the centre of the galaxy travelling much faster than those further out. Two constants derived by Oort – known as

Oort constants A and B – underpinne­d this realisatio­n and are still used in calculatio­ns of galactic rotation to this day. Through studying the motion of stars, Oort also revealed that our Sun was not at the centre of the Milky Way, but was in fact some 26,000 light years out in the galactic suburbs. Moreover, during his observatio­ns of star movement throughout our galactic home, Oort used the term ‘dark matter’ to describe the unidentifi­ed mass causing stars to move faster than calculatio­ns had predicted.

Ever perceptive, Oort was one of the first scientists to realise the true significan­ce of using radio waves to investigat­e the cosmos. He theorised that clouds of hydrogen gas were loitering out in the spiral arms of the Milky

Way, and it was in these gaseous plumes that stars were born. Oort predicted this before radio telescopes were able to confirm his theories. After World War II he was able to witness his ideas and theories become reality at the new Dutch radio observator­ies Dwingeloo and Westerbork.

One of his most notable contributi­ons to astronomy is his theory that a vast reservoir of comets surrounds the Solar System. Though yet to be proven, his theory is widely accepted within the scientific community and has come to be known as the Oort Cloud. Oort had meticulous­ly studied the orbits of long-period comets, noticing that many originated from a zone far beyond the orbit of Pluto. Encompassi­ng the Solar System in a giant spherical shell, the

Oort Cloud is thought to contain billions – if not trillions – of pieces of icy space debris and is home to most of the long-period comets we observe in our Solar System. Oort quite literally rewrote the textbooks on galactic motion and our understand­ing of the universe.

Born in Franeker in the Netherland­s, Oort attended the University of Groningen, where he enrolled at the age of 17 to study astronomy. After graduation he continued to work at the University of Groningen as an assistant for a year, then headed to the US to gain experience working at Yale Observator­y for two years.

In 1924 Oort returned to the Netherland­s, achieving his doctorate with a thesis titled ‘The Stars of High Velocity’ just two years later. Oort’s research continued throughout World War II, and when the war ended he became the director of the Leiden Observator­y, holding this position from 1945 to 1970. During this time Oort was also the general secretary of the Internatio­nal Astronomic­al Union, serving from 1935 to 1948. Throughout his career Oort won many coveted awards, one of the more prestigiou­s being the Vetlesen Prize from Columbia University, which he won in 1966.

Oort passed away in 1992 at the age of 92.

His revolution­ary ideas and discoverie­s which shook the scientific world continue to shape our understand­ing of the universe to this day.

“Oort also revealed that our Sun was not at the centre of the Milky Way”

 ??  ?? Oort postulated dark matter in galaxies
Oort postulated dark matter in galaxies

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