The scientific consensus strongly supports the existence of a supermassive black hole at the center of our Milky Way galaxy. This black hole is commonly referred to as Sagittarius A* (Sgr A*). The evidence for its existence comes from multiple lines of observation and has been gathered over several decades.
Here are some key lines of evidence supporting the existence of the supermassive black hole in the center of the Milky Way:
Stellar Orbits: Astronomers have tracked the motion of stars near the center of the galaxy. These stars orbit an invisible and extremely massive object, indicating the presence of a compact gravitational source. The observed motion of these stars can be explained by the gravitational influence of a supermassive black hole.
Gas Dynamics: Gas clouds near the galactic center exhibit strong and coherent motion. By studying the movement and velocity of these gas clouds, scientists have inferred the presence of a massive and compact object at the center, consistent with a black hole.
X-ray and Radio Emission: Observations in X-ray and radio wavelengths have detected intense radiation emanating from the galactic center. This emission is thought to arise from the accretion of matter onto a black hole. The properties of this emission match the characteristics expected from a supermassive black hole.
Gravitational Wave Detection: In 2015, the LIGO (Laser Interferometer Gravitational-Wave Observatory) collaboration detected gravitational waves for the first time, caused by the merger of two black holes in a distant galaxy. Similar mergers are expected to occur, including those involving supermassive black holes. While direct evidence for the Milky Way's supermassive black hole from gravitational waves is challenging due to its lower frequency, future gravitational wave observatories may provide more insights.
Based on these observations, it is estimated that Sagittarius A* has a mass of about 4 million times that of our Sun. Its size is characterized by its event horizon, which is a theoretical boundary beyond which nothing can escape. The event horizon of Sagittarius A* is believed to have a radius of around 12 million kilometers (7.5 million miles).
As for the age of Sagittarius A*, it is challenging to determine precisely. However, it is generally believed that supermassive black holes like Sgr A* form and grow over long periods of time, likely evolving alongside their host galaxies. The age of Sgr A* is therefore thought to be comparable to the age of the Milky Way, which is estimated to be around 13.6 billion years.
It's important to note that while there is strong scientific consensus regarding the existence of Sgr A* based on current observations, ongoing research and future observations will continue to refine our understanding of this fascinating object at the heart of our galaxy.