What is a star and how is it formed?

 A star is a luminous celestial object composed of hot plasma (a state of matter consisting of charged particles) held together by its own gravity. Nuclear fusion reactions occur in stars' cores, which produce light and heat.

During the formation of a star, gas and dust meet in a molecular cloud, forming a molecular cloud. These clouds are primarily composed of hydrogen, with traces of other elements. The collapse of a molecular cloud can be triggered by many factors, including shockwaves coming from a nearby supernova or gravitational interaction between neighboring clouds.

As the molecular cloud collapses, the pressure and temperature of the gas increase, causing the formation of a protostar. The protostar then continues to collapse until nuclear fusion begins and the star is born.

A Cloud breaks down into smaller gas and dust clumps, creating a protostar. As it contracts, it converts gravitational potential energy into thermal energy. This causes the protostar to heat up and become denser and hotter over time.

At 10 million degrees Celsius, nuclear fusion begins, causing hydrogen atoms to fuse to form helium. This reaction releases energy in the form of light and heat, counteracting gravity's force and maintaining the star's stable state. This equilibrium between gravity pulling inward and fusion energy pushing outward maintains star stability.

As the core continues to heat up, the reaction rate increases. This causes the production of more helium and more energy, which further strengthens the outward pushing force. This continues until the star can no longer generate enough energy to counteract gravity's force, and the star begins to collapse.

Star size, mass, and composition determine its lifespan and eventual fate. It burns steadily for billions of years until hydrogen fuel exhausts. At this point, it may undergo fusion, transforming helium into heavier elements like carbon and oxygen. Stars can end their lives in various ways, such as becoming white dwarfs, neutron stars, or supernova explosions, leaving behind remnants like black holes.

As the star continues to age, it can no longer produce enough energy to sustain itself, resulting in some of the most spectacular events in the Universe.