Sagittarius A* is a bright and very compact astronomical radio source at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5. 6° south of the ecliptic. Based on mass and increasingly precise radius limits, astronomers have concluded that it is the Milkyway’s central supermassive black hole.
About Sagittarius A* in brief
Sagittarius A* is a bright and very compact astronomical radio source at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5. 6° south of the ecliptic. Based on mass and increasingly precise radius limits, astronomers have concluded that it is the Milkyway’s central supermassive black hole. Reinhard Genzel and Andrea Ghez were awarded the 2020 Nobel Prize in Physics for their discovery that Sgr A*. is a supermassive compact object, for which a black hole is the only currently known explanation. If discrepancies between the theory of relativity and observations are found, scientists may have identified physical circumstances under which the theory breaks down. In 2019, measurements made with the High-resolution Airborne Wideband Camera-Plus revealed that magnetic fields cause the surrounding ring of gas and dust, temperatures of which range from −280 °F to 17,500 F, to flow into an orbit around Sagittius A*, keeping black hole emissions low. The current highest-resolution measurement, made at a wavelength of 1. 3 mm, indicated an overall angular size for the source of 50 μas. At a distance of 26,000 light-years, this yields a diameter of 60 million kilometres. The proper motion of Sgr A* is approximately −2. 70 mas per year for the right ascension and −5. 6 mas per year for the declination.
The Event Horizon Telescope uses interferometry to combine images taken from widely spaced observatories at different places on Earth in order to gain a higher picture resolution. In 2017, direct radio images were taken of Sagittarus A* and M87* by the Event Horizon telescope. According to the team’s analysis, the data ruled out the possibility that SGr A* contains a cluster of dark stellar objects or a mass of degenerate fermions, strengthening the evidence for a massive black Hole. The name Sgr* was coined by Brown in a 1982 paper because the radio source was \”exciting\”, and excited states of atoms are denoted with asterisks. On October 16, 2002, an international team reported the observation of the motion of the star S2 near Sagittaria A* throughout a period of ten years. From examining the mass of S2, they determined the object to be 2.6±0.4 million solar masses. Later observations showed a star of the same orbit to be about 1 million solar masses within the orbit of the object. The VLBI could also be found to coincide with the position of the Sagittarian A*. It is hoped the measurements will test Einstein’s theory of relativity more rigorously than has previously been done. It’s hoped that the data will also prove the existence of black holes in other galaxies, such as the Andromeda Galaxy and the Crab Nebula in the constellation Cygnus.