1922 - 1

Ernst Öpik was the first to establish the distance of the Andromeda nebula, thus proving the location of galaxies outside the Milky Way.

The Estonian astronomer Ernst Öpik (1893-1985) was one of the most famous and many-sided scientists of the world in the 20th century. His scientific research includes different themes starting from the observation of meteorites to cosmology. His pioneering research very often relies on excellent scientific instinct and he reached discoveries, always following constant logic and clear and simple calculations.

One of his most important contributions was to establish the distance of a galaxy for the first time and as a result he solved the long-term problem of the cosmological distance. Even in the second decade of the 20th century the discussion in astronomy whether nebulae were the objects of the Milky Way or distant galaxies was under way. The American astronomer Edwin Hubble established the distance of the Andromeda nebula in 1924 using for this purpose the distance of the stars which periodically changed their brightness – Cepheid variables. At that time the honor of solving the problem belonged to Hubble but already in 1918 (published in 1922) Öpik had established the distance of the Andromeda nebula even more accurately using the dynamics of Andromeda and proving the location of galaxies outside the Milky Way (according to Öpik the distance of Andromeda is 450 kilo parsecs, at present it is estimated 770 kilo parsecs. Öpik’s priority was later recognized thanks to his fame in more senior age.

The Andromeda nebula – galaxy M31

1922 - 2

Ernst Öpik presented his idea of thermonuclear energy as the inner source of energy of stars.

At the beginning of the 20th century astrophysics had reached the theory of the appearance and the evolution of stars in which Arthur Eddington played the most important role. Studying the statistical distribution of the brightness of stars, Öpik showed that the inner energy of stars comes mainly from thermonuclear energy and not from gravitational cooling.

Ernst Öpik (TO)