Sagittarius A
Radio source at the center of the Milky Way galaxy
Sagittarius A, abbreviated as Sgr A, is a complex radio source at the center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, though it is hidden from view at optical wavelengths by large clouds of cosmic dust in the spiral arms of the Milky Way. The dust lane that obscures the Galactic Center from a vantage point around the Sun causes the Great Rift through the bright bulge of the galaxy.
The radio source consists of three components: the supernova remnant Sagittarius A East; the spiral structure Sagittarius A West; and the supermassive black hole Sagittarius A*, the source of the strongest radio emissions. Sagittarius A* is located at the center of Sagittarius A West, while Sagittarius A West appears off-center within Sagittarius A East. Sagittarius A East is by far the largest of the three.
Discovery
In April 1933, Karl Jansky, considered one of the fathers of radio astronomy, discovered that a radio signal was coming from a location in the direction of the constellation of Sagittarius, towards the center of the Milky Way. His observations did not extend quite as far south as we now know to be the Galactic Center. Observations by Jack Piddington and Harry Minnett using the CSIRO radio telescope at Potts Hill Reservoir, in Sydney discovered a discrete and bright "Sagittarius-Scorpius" radio source, which after further observation with the 80-foot (24-metre) CSIRO radio telescope at Dover Heights was identified in a letter to Nature as the probable Galactic Center. The name Sagittarius A was first used in 1954 by John D. Kraus, Hsien-Ching Ko, and Sean Matt when they included the object in the list of radio sources found with the Ohio State University radio telescope at 250 MHz.
This brief starts where responsible research should: with the source description of “Sagittarius A” as radio source at the center of the Milky Way galaxy. Everything that follows is an evidence route, not borrowed authority.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 31, 2026. The linked authority identifier is Q237291. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1933 and 1954.
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This entry incorporates text from “Sagittarius A” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.