Interesting to note that there are quite a few nearer than Sagittarius A, as of 2022 we know of one at 1.5 kly: universemagazine.com/en/discovered-the-closest-black-hole-to-the-sun/
It is interesting that a few months earlier there seemed to be no known specific black holes in the Milky Way: www.nasa.gov/feature/goddard/2022/hubble-determines-mass-of-isolated-black-hole-roaming-our-milky-way-galaxy although their count is estimated to be in the hundreds of millions.
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A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. This phenomenon occurs when a massive star collapses under its own gravity at the end of its life cycle. Black holes are characterized by three main properties: 1. **Singularity**: At the center of a black hole lies the singularity, a point where gravity is thought to be infinitely strong, and known laws of physics break down.