Antonie “Anton” Pannekoek (; 2 January 1873 – 28 April 1960) was a Dutch astronomer, philosopher, Marxist theorist, and socialist revolutionary. He was one of the main theorists of council communism ().
Biography
Pannekoek studied mathematics and physics in Leiden from 1891. Even before he went to college he was interested in astronomy and studied the Milky Way and variability of Polaris. He published his first article, On the Necessity of Further Researches on the Milky Way, as a student. He briefly worked as a geodesist before he returned to the Leiden Observatory () to work as an observer and write his thesis on the variability of Algol.
After reading Edward Bellamy's Equality, Pannekoek became a convinced socialist and started studying the philosophies of Karl Marx and Joseph Dietzgen. Soon Pannekoek became a well-known Marxist writer, writing for both Dutch and German socialist magazines, like Die Neue Zeit. His astronomical and socialist careers first clashed when he was reprimanded for leading a strike support committee and was treated with dismissal from his job at the observatory by the Dutch government. Around the same time, he was growing dissatisfied with the stale atmosphere and outdated methodologies at the Leiden Observatory. Pannekoek was offered the option to become a lecturer in historical materialism at the school funded by the Social Democratic Party of Germany. He soon ran into trouble with the German authorities, who threatened him with expulsion if he continued teaching. He remained in Berlin, however, where he kept writing for journals and newspapers. In 1910, he moved to Bremen where he soon became one of the prominent proponents of the radical Bremen Left.
Pannekoek was on holiday in the Netherlands when the First World War broke out. Prevented from returning to Germany, he started work as a cosmography and science teacher for secondary schools and a privaatdocent in history of astronomy at Leiden University. Though Willem de Sitter wanted to hire him as assistant director at the Leiden Observatory in 1918, the appointment was prevented by the Dutch government because of his outspoken Marxist sympathies. Instead, the Amsterdam city council appointed him at the University of Amsterdam in 1918 as a lecturer. In 1921, he founded the astronomical institute there; in 1925, he was appointed as extraordinary professor; and in 1932 as full professor.
Astronomy
Pannekoek began systematically observing the night sky and recording these observations while he was still in secondary school. Some of his observations of variable stars later found their way into his scientific publications. In the winter of 1889–1890, he recorded the variability of Polaris, which had been suspected before but was not confirmed until 1908 by Ejnar Hertzsprung. He also tracked the variability of Algol, which formed the foundation for his PhD thesis.
Another early interest of Pannekoek was the appearance of the Milky Way. In 1898, Pannekoek published a series of articles in which he articulated how he thought the Milky Way should be observed. Here, he explained that minor details should be tracked through verbal descriptions, while the general distribution of light should be tracked to isophotic lines. Pannekoek published his own observations of the northern Milky Way in 1920 in the form of drawings, isophotic diagrams, and verbal descriptions. He also combined his observations the independent observations of Cornelis Easton, Otto Boeddicker, and Julius Schmidt to create a composite image of the Milky Way, which he called the "mean subjective image". A few years later, he also published his observations of the southern Milky Way, which he made during an eclipse expedition to the Dutch Indies in 1926. He also developed a photographic method to represent the light distribution of the Milky Way. To capture the clouds that formed the Milky Way, Pannekoek deliberately recorded photographic plates out of focus, which caused the light of stars to spread into disks, allowing their light to overlap. These plates were then measured and combined into tables showing the surface brightness of the Milky Way.