Leiden astronomer Jan Oort discovered that comets – large rocks from space – don’t just appear in the Universe out of nowhere. He observed that they originate in a circle-shaped ‘cloud’ in the outer regions of our solar system.
The fact that Oort was a leading scientist is apparent from the fact that he has not one, but three major astronomical breakthroughs to his name. In addition to his clarification of the structure of the Milky Way and his impact on the rise of radio astronomy, Jan Oort was also the first to discover where comets in our solar system come from.
Oort cloud
In 1950 Oort established that there is a cloud at the outer edge of our solar system that contains a gigantic collection of comets. It is there, where the Sun is no more than a bright star, that these space rocks orbit around the Sun. Due to their long orbits around the Sun, they remain far away for a long time, and then suddenly appear nearby. The cloud containing these comets is known to this day as the Oort cloud.
This is only one of the discoveries which brought Jan Oort world fame. In 1932, he was also the first to establish that there must be something like dark matter – an invisible form of matter, the existence of which astronomers could only establish indirectly. Dark matter is one of the most important research topics in modern astronomy.
Great oak
Oort became so famous as a researcher that in 1955 the American magazine Life selected him for its list of the ‘100 most famous people alive’. When Oort died in 1992, the Indian-American astronomer Subramanyan Chandrasekhar responded as follows: ‘The great oak of Astronomy has been felled; and we are lost without its shadow’. In an ‘In Memoriam’ in the renowned American newspaper The New York Times, Jan Oort was referred to as the greatest astronomer of the 20th century.
