Antonie Pannekoek

Born Jan. 2, 1873, in Vaassen; died Apr. 28, 1960, in Amsterdam. Dutch astronomer. Member of the Netherlands Academy of Sciences (1925). Active in the Dutch workers’ movement.

Pannekoek was first a lecturer (1918–25) and then a professor of astronomy (1925–42) at the University of Amsterdam. In 1920 he developed a method of determining distances to dark nebulae and in 1921 studied the surface brightness of the Milky Way, disregarding the influence of interstellar light absorption. He was one of the first astronomers (in 1922 and 1926) to study the process of ionization in stellar atmospheres.

Pannekoek was involved in the workers’ movement at the beginning of the 20th century. In 1902 he became a member of the Social Democratic Workers’ Party of the Netherlands. In 1907 he helped found the left-wing Social Democratic paper De Tribune, and, together with other “tribunists,” he founded the Social Democratic Party of the Netherlands in 1909. From 1905 to 1914 he taught at the party school of the German Social Democrats in Berlin and was associated with the left wing of the German Social Democratic Party. He remained an internationalist during World War I and was involved in the publication of the journal Vorbote, organ of the Zimmerwald left. From 1918 to 1921 he was a member of the Communist Party of the Netherlands and until 1921 was active in the Comintern. He was one of the leaders of the ultraleft German Communist Workers’ Party (under the pseudonym K. Horner) and was sharply criticized by V. I. Lenin in “‘Left-wing’ Communism, an Infantile Disorder.”