Born in Estonia, Öpik did his graduate studies at the University of Moscow and specialized in the study of comets and asteroids. After the 1917 revolution, he participated in the creation of the University of Tashkent, and then returned to Estonia where he remained until 1944. He then fled the Red Army and after various vicissitudes joined the observatory of Armagh in Northern Ireland in 1948. After 1960, he divided his time between this observatory and the University of Maryland in the United States. His works are varied and imaginative, ranging from stellar physics to that of meteors. The best known is his idea of the existence of a reservoir of comets far from the Sun.