Wikipedia article of the day for July 17, 2026

The Wikipedia article of the day for July 17, 2026 is Black hole.
A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Black holes typically form when massive stars collapse at the end of their life cycle. In general relativity, crossing a black hole's event horizon traps an object inside but produces no locally detectable change. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century. In 1916, the first solution of general relativity that would characterise a black hole was found. The presence of a black hole can be inferred through its interaction with matter and electromagnetic radiation. The first widely accepted black hole was Cygnus X-1, identified in 1971. Astronomers have since identified numerous stellar black hole candidates in binary systems and established that Sagittarius A*, a compact radio source at the core of the Milky Way, is a supermassive black hole of about 4.3 million solar masses.