Galactocentrism

Shapley had been studying the asymmetrical distribution of globular clusters, estimating the distance and location of individual objects by using variable stars as standard candles. Globular clusters contain many cepheid variable stars, whose precise relationship between luminosity and variability period was established by Henrietta Leavitt in 1908. The Galactic Center was determined to be in the direction of the Sagittarius constellation, approximately 50,000 light-years from us. When astronomers realized that starlight can be absorbed by clouds of gas and dust, infrared radiation was used to penetrate the dust clouds. Estimates dating after 2000 locate the Solar System within the range from the Galactic Center of the Milky Way galaxy. == Shift from galactocentrism to acentrism ==

Hubble's observations of redshift in light from distant galaxies indicated that the universe was expanding and acentric. As a result, galactocentrism was abandoned in favor of the Big Bang model of the acentric expanding universe. Further assumptions, such as the Copernican principle, the cosmological principle, dark energy, and dark matter, eventually lead to the current model of cosmology, Lambda-CDM. ==References==