Mass of black hole in milky way
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Mass of the Black Hole in the Milky Way
Supermassive Black Hole at the Galactic Center
The Milky Way galaxy harbors a supermassive black hole (SMBH) at its center, known as Sagittarius A* (Sgr A*). Observations of stellar orbits around Sgr A* provide compelling evidence for this SMBH. High-resolution astrometric imaging over a decade has traced the orbit of a star around Sgr A*, revealing a highly elliptical Keplerian orbit with a period of 15.2 years. This data indicates a central mass of approximately 3.7 million solar masses (M☉) . Further studies have confirmed that the mass of the SMBH at the center of the Milky Way is about 4 million M☉, based on the motion of stars within a radius of 100 AU from Sgr A* .
Evidence from Stellar Velocities and X-ray Emissions
The presence of the SMBH is also supported by measurements of stellar velocities and variable X-ray emissions. These observations have ruled out alternative mass concentrations, reinforcing the conclusion that a supermassive black hole resides at the center of our galaxy 27. The compact radio source Sgr A* is nearly motionless at the dynamical center of the Galaxy, further supporting the existence of the SMBH .
Intermediate-Mass Black Holes in the Milky Way
In addition to the SMBH, the Milky Way may contain numerous intermediate-mass black holes (IMBHs). These IMBHs, with masses ranging from 100 to 1000 M☉, are thought to be enshrouded by dense dark minispikes and minihalos. Some of these IMBHs are located within a few kiloparsecs of the Galactic center and are largely invisible except for their potential neutralino annihilation signals . One candidate IMBH, with a mass of about 100,000 M☉, has been identified near Sgr A* based on extreme gas kinematics observed in a molecular cloud .
Population of Stellar-Mass Black Holes
The Milky Way also hosts a significant population of stellar-mass black holes. A synthetic catalog estimates that the galaxy contains approximately 1.2 × 10^8 single black holes with an average mass of about 14 M☉, and 9.3 × 10^6 black holes in binary systems with an average mass of 19 M☉ . These black holes play a crucial role in the dynamics of globular clusters, influencing their evolution and structure .
Conclusion
The central black hole of the Milky Way, Sagittarius A*, has a well-established mass of around 4 million solar masses. This supermassive black hole is a key feature of our galaxy, influencing the motion of nearby stars and emitting detectable X-ray and radio signals. Additionally, the Milky Way contains numerous intermediate and stellar-mass black holes, contributing to the complex gravitational landscape of our galaxy.
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