Stars and Galaxies: Life Cycles of Stars

Stars undergo a life cycle starting from a nebula, where dust and gas form a protostar. Depending on their mass, stars can live for billions of years. As they age, they expand into giants or super giants. When they exhaust their fuel, they become white dwarfs, neutron stars, or black holes. Neutron stars result from supernova explosions, while the most massive stars collapse into black holes, where gravity is so strong that not even light can escape.

What are the possible forms a star can take after it runs out of fuel?

Explain the characteristics of black holes.