Black holes are the result of a massive star collapsing under its own weight at the end of its life, leaving behind a gravitational anomaly so strong that not even light can escape. The edge of a black hole is defined as being an event horizon, the point beyond which nothing can return once it has passed. While exceedingly dangerous, black holes are a fundamental building block of the universe's structure, serving as the center of many galaxies including our own. The Milky Way's central supermassive black hole is known as Sagittarius A* and has a mass of 4.3 million solar masses.
For the past 3,000 years, black holes have found themselves as a very useful asset for solspawn civilization's energy production, often being the site of gargantuan megastructures known as Penrose stations (after 20th-21st century physicist Roger Penrose). Furthermore, production of artificial miniature black holes has been possible since the 51st century and has opened up the horizons for black hole power even further.