In astronomy, galactocentrism is the theory that the Milky Way Galaxy, home of Earth's Solar System, is at or near the center of the Universe.[1][2]
Thomas Wright and Immanuel Kant first speculated that fuzzy patches of light called nebulae were actually distant "island universes" consisting of many stellar systems.[3] The shape of the solar system's own parent galaxy was expected to resemble such "islands universes," but "scientific arguments were marshalled against such a possibility," and this view was rejected by almost all scientists until Edwin Hubble's measurements in 1924.[4]
William Herschel's heliocentric model of the universe, which was regarded as the standard model of cosmology in the 19th century, was overthrown by astronomer Harlow Shapley's work on globular clusters in 1918. Shapley's research marked the transition from heliocentrism to galactocentrism,[5][6][7] placing the Galactic Center of the Milky Way Galaxy far away from the Sun, towards Sagittarius. Heber Doust Curtis and Edwin Hubble further refuted the heliocentric view of the universe by showing that spirals are themselves far-flung galactic systems. By 1925, the galactocentric model was established.[7]
The theory of galactocentrism was an important step in the development of cosmological models as speculation on the existence of other galaxies, comparable in size and structure to the Milky Way, placed the Earth in its proper perspective with respect to the rest of the universe. Shifts from heliocentrism to galactocentrism and later acentrism have been compared in significance to the Copernican Revolution.[7]