Sagittarius A* (pronounced "Sagittarius a star") is the supermassive black hole at the center of the Milky Way galaxy. It has a mass equivalent to about four million Suns and is a very compact and bright astronomical radio source located in the constellation Sagittarius. Sagittarius A* is surrounded by stars orbiting it, providing strong evidence of its nature as a black hole. It was first discovered through radio observations and more recently imaged using the Event Horizon Telescope, revealing the glowing gas around the black hole and its gravitational effects. This object is the closest known supermassive black hole to Earth, about 26,000 light years away.
Key Facts about Sagittarius A*
- It is a supermassive black hole at the Galactic Center of the Milky Way.
- Mass is approximately 4 million times that of our Sun.
- Located near the constellation Sagittarius, visually close to the Butterfly Cluster and Lambda Scorpii.
- Detected primarily as a bright compact radio source.
- The Event Horizon Telescope has produced the first direct image of its surrounding accretion disk.
- The black hole itself cannot be seen directly, as its gravity prevents light escape.
- Stars orbiting Sagittarius A* (notably star S2) have been used to calculate its mass and confirm the black hole's existence.
- The discovery and study of Sagittarius A* earned the 2020 Nobel Prize in Physics.
This "star" in its name is not a normal star but rather a naming convention, where the asterisk (*) denotes a bright, compact radio source.
