Ernst Julius Öpik (22 October [O.S. 10 October] 1893 – 10 September 1985) was an Estonian astronomer and astrophysicist who spent the second half of his career (
Ernst Julius Öpik (22 October [O.S. 10 October] 1893 – 10 September 1985) was an Estonian astronomer and astrophysicist who spent the second half of his career (1948–1981) at the Armagh Observatory in Northern Ireland.
22 October 1893|
Kunda, Lääne-Viru, Estonia
|Died||10 September 1985
Bangor, Northern Ireland, United Kingdom
Öpik was born in Kunda, Lääne-Viru, Governorate of Estonia, Russian Empire. He went to the University of Moscow to specialize in the study of minor bodies, such as asteroids, comets, and meteors. He completed his doctorate at the University of Tartu.
In 1916 Öpik published an article in the Astrophysical Journal, in which he estimated the densities of visual binary stars. In his sample was ο2 Eridani, a white dwarf star. Öpik determined its density as 25,000 times the density of the Sun but concluded that the result is impossible.
In 1922, Ernst Öpik published a paper in which he estimated the distance of the Andromeda Galaxy. He determined the distance using a novel astrophysical method based on the observed rotational velocities of the galaxy, which depends on the total mass around which stars are rotating, and on the assumption that the luminosity per unit mass was the same as that of our galaxy. He concluded that the distance was 450 kpc. His result was in good accordance with other estimates of these days (100 to 1000 kpc) and were closer to recent estimates (778 kpc) than Hubble's result (275 kpc). His method is still widely used.
In 1922 he correctly predicted the frequency of craters on Mars long before they were detected by space probes. In 1932 he postulated a theory concerning the origins of comets in our solar system. He believed that they origin