Sagittarius A (abbreviated as Sgr A) is a radio source in the constellation Sagittarius. It is located at the center of our Milky Way galaxy. In 1974, it was discovered to be a supermassive black hole by astronomers using radio telescopes.
The mass of Sagittarius A* has been measured to be about 4 million times that of our Sun. It is one of the most massive known black holes. It is also one of the closest black holes to Earth, at a distance of only 25,000 light years.
Sagittarius A* is surrounded by a cloud of gas and dust known as the accretion disk. As material from the accretion disk falls into the black hole, it releases energy in the form of X-rays and gamma rays. These high-energy emissions make Sagittarius A* one of the brightest X-ray sources in our sky.
Astronomers believe that almost all galaxies have supermassive black holes at their centers. The study of Sagittarius A* can help us better understand how these giant objects form and grow over time.