Black holes are extremely dense objects in space with gravitational forces so strong that nothing, not even light, can escape their gravitational pull. They are formed from the remnants of massive stars that have undergone gravitational collapse.
Yes, there are known stars that are believed to have black holes in their systems. These black holes are typically formed when a massive star exhausts its nuclear fuel and undergoes a supernova explosion. The remaining core collapses under its own gravity, forming a black hole.
One famous example is the Cygnus X-1 system. Located in the constellation Cygnus, it consists of a blue supergiant star called HDE 226868 and a black hole. Cygnus X-1 was the first stellar-mass black hole ever discovered and has been extensively studied.
However, it's important to note that black holes themselves are not directly visible since they do not emit light. We can only infer their presence through their gravitational effects on nearby objects, such as their companion stars. So, you won't be able to spot black holes on a night sky map. The stars in these systems, on the other hand, may be visible depending on their brightness and your location.
If you're interested in observing celestial objects, I can provide information about visible stars, constellations, and other fascinating features of the night sky.