Taavet Rootsmäe (27 June 1885 Tartumaa – 27 June 1959 Tartu) Director in 1919−1948

Taavet Rootsmäe (until 1936 David Rootsman) was born on the Roosa farm in the rural municipality of Kastre-Võnnu to the family with many children. Although his parents hoped that their son could be a secretary of the municipality, Taavet Rootsmäe already in his childhood was greatly interested in nature and the starry sky.

Rootsmäe received his secondary education at the Hugo Treffner Gümnaasium (secondary school) in Tartu. For the scarce support money from parents at school he bought mainly books. When studying in Tartu, he built a small telescope for himself; he attached it to the chimney on the roof and made observations at night.

In 1906 Rootsmäe began to study at the Faculty of Physics and Mathematics of Tartu University and devoted himself fully to astronomy. In 1913 he defended his candidate thesis about the research of the movement of the small planet WF-1906. After graduating from the university Rootsmäe worked in Tallinn for six years as a teacher of mathematics, physics and astronomy. In 1919 Rootsmäe was invited to occupy the post of the professor of Tartu University and the director of Tartu Observatory. Rootsmäe remained the university professor until his death, As the director of the observatory he could work until 1948 when the Tartu Observatory was subordinated to the Academy of Sciences of the Estonian SSR. In the observation complex he could continue using his room where he could receive students and give advice to the employees of the observatory – his former disciples.

The main fields of Rootsmäe’s research were stellar astronomy, theoretical astronomy, the celestial mechanics, general astronomy and the theory of errors. He presented statistical criteria for the determination of the age of the stars on the basis of their movement and he applied these results for describing the evolution of the stellar system. Rootsmäe contributed much to creating and perfecting the astronomical terminology in the Estonian language. Together with Ernst Öpik he is the founder of the scientific school of Estonian astronomy. Taavet Rootsmäe wrote several textbooks of astronomy for Estonian schools, popularized science by delivering interesting lectures and publishing popular-science articles for magazines. Being extremely self-critical and profound, the number of Rootsmäe’s published scientific articles is small and much of the collected material was not presented in the form of articles.