Which galaxy contains the supermassive black hole Sagittarius A*?

The galaxy containing the supermassive black hole Sagittarius A* is the Milky Way.

Sagittarius A* lies at the centre of our home galaxy, in the direction of the constellation Sagittarius. It is about 26,000 light-years from Earth and has a mass of approximately 4.3 million Suns. Although it is enormous by everyday standards, it is far smaller than the black hole at the centre of Messier 87.

Astronomers established its mass by tracking the orbits of stars close to the galactic centre. One especially useful star, called S2, completes an elongated orbit in roughly 16 years and reaches a very high speed near its closest approach.

The asterisk in Sagittarius A* is part of the astronomical name and does not mean a footnote. The compact radio source was first identified in the 1970s, while the EHT released its image in 2022. The surrounding gas changes quickly because the black hole is relatively small in astronomical imaging terms.