A stellar black hole is a type of black hole formed when a massive star exhausts its nuclear fuel and collapses under its own gravity. This process typically occurs after the star has gone through a supernova explosion, leaving behind a core that can become incredibly dense. If the core's mass exceeds about three times that of the Sun, it will collapse into a black hole. Stellar black holes can vary in size, usually ranging from about 3 to 20 solar masses. They are often detected by observing the effects of their strong gravitational pull on nearby stars and gas. When matter falls into a stellar black hole, it forms an accretion disk, emitting X-rays that can be detected by telescopes.