1902 — Albert Michelson clarifies the speed of light (299,890 ± 60 km/s).
1908 — the first extraterrestrial object — the Sun — discovered a magnetic field (George Hale).
1908-1916 — the discovery of a directly proportional relationship between the period and the apparent magnitude of the cepheids in the Small Magellanic Cloud (Henrietta Leavitt, USA). Guided by this discovery, Einar Hertzsprung and Harlow Shapley developed a method for determining distances by cepheids.
1912 — the discovery of cosmic rays (Hess, Kohlhurst).
1913 — unusually large redshifts were detected in spiral nebulae (Vesto Slipher, USA).
1914-1919 — the theory of pulsation of cepheids by Harlow Shapley and Arthur Eddington.
1916 — Barnard's "flying" star was discovered (Edward Barnard, USA).
1916-1918 — the theory of the internal structure of stars by Arthur Eddington.
1918 — Harlow Shapley's model of the structure of the Galaxy, derived from observations; the diameter and position of the center were correctly determined; unexpectedly for everyone it turned out that the Sun is on the edge of the Galaxy.
1919 — creation of the International Astronomical Union.
1923 — the discovery of the 22-year cycle of magnetic activity of the Sun and the change of the sign of the polarity of spots (George Hale, USA). Establishing the mass-luminosity relationship for stars — Einar Hertzsprung (Denmark), Ressel (USA), Arthur Eddington (England).
1924-1926 — the theory of radiant equilibrium of the stellar interior by Arthur Eddington.
1925-1934 — discovery of carbon dioxide on Venus (Adams, St. John and Dunham, USA).
1926-1927 — based on the analysis of the motion of stars, Bertil Lindblad and Jan Oort establish the rotation of the Galaxy.
1927 — Georges Lemaitre publishes his hypothesis of the expansion of the Universe.
1929 — Hubble's law was established.
1930, February 19, Pluto was discovered by Clyde Tombaugh, USA.
1931 — Arthur Milne's hypothesis — a white dwarf remains after the nova explosion.
Early 1930s - Fritz Zwicky makes a conclusion about the existence of a hidden mass in the universe.
1934 — Pavel Parenago and B. V. Kukarkin predict the flare of the star T of the Northern Corona; it really happened in 1946.
1934 — Walter Baade and Fritz Zwicky suggest that a neutron star remains after a supernova explosion.
1942 — Mayall and Jan Oort find out that the Crab Nebula is a remnant from the supernova explosion of 1054. The first radio map of the sky (Edges) has been compiled.
1945 — the red shift was confirmed in the radio range (M. Ryle, England).
1950 — the Oort hypothesis about the existence of a spherical layer of comets at the edge of the Solar System (100-150 thousand AU) — the "Oort cloud".
1951 — the spiral structure of our Galaxy is proved.
1955-1956 — registration of radio emissions of Venus, Jupiter and comet Rent—Rolland.
1957 — the launch of the first artificial Earth satellite (Sputnik-1), the beginning of the space age. The possibility of creating space laboratories has appeared.
1958 — the discovery of the Van Allen radiation belts. Nikolai Kozyrev notes signs of volcanic activity in the lunar crater Alphonsus, which, however, have been refuted from a modern point of view.
1959 — Solar radar (USA). The Luna-2 station does not detect a magnetic field near the Moon. The first photos of the reverse side of the Moon have been obtained.
1961 — the first human flight into space.
1961-1964 — radar of Mercury, Venus, Mars, Jupiter (USSR and USA). The value of a. e. and the period of rotation of Venus around the Sun are specified, the period of axial rotation of Venus (it turned out to be the opposite), temperature and physical characteristics of the surface of the planets are determined.
1965 — the discovery of relic radiation. The first photos of the surface of Mars (Mariner-4).
1967 — the first study of the atmosphere of Venus from the lander (Venus-4).
1969 — Apollo 11 landing on the moon. The first human appearance on the surface of the moon.
1971 — the first soft landing on Mars (Mars-3).
1971 — the first photos of the surface of Phobos and Deimos Mariner-9.
1974 — Stephen Hawking's sensational conclusion about the possibility of "evaporation" of black holes.
1975 — the first photopanorama of the surface of Venus (Venus-9.10).
1975 — photos of Phobos, Deimos and the surface of Mars (Viking-1, Viking-2).
1977 — the discovery of the rings of Uranus. The launch of Voyager 2, which transmitted invaluable information about the outer planets: Jupiter, Saturn (1981), Uranus, Neptune (1989).
1978 — the discovery of Charon, a satellite of Pluto (J. W. Christie, USA).
1979 — rings were discovered near Jupiter.
1986 — study of Halley's comet by AMS Vega and Giotto. Uranus has discovered 10 new satellites.