What is Stellar Evolution?
Stellar evolution describes the process in which stars form, burn for an extended period of time, and eventually die. Along the way, the star struggles with gravity and fuel consumption in an attempt to maintain equilibrium. Much of stellar evolution is theory, since humans have not been around long enough to observe the entire life cycle of a single star, but thanks to the ample numbers of stars at various stages scattered around the universe, it has been possible to make educated and intelligent guesses about how stars evolve over time, and the process appears to be relatively predictable. The process of stellar evolution starts with the formation of a star. Stars form in what are known as “giant molecular clouds,” swirling masses of gases and particles. Over time, these clouds undergo gravitational collapse, generating protostars, celestial bodies which have the potential to become stars. The type of star that a protostar will evolve into depends on its chemical composition. As the
Let us provide a definition from an unbiased source: “Stellar evolution is the series of phases that a star passes through between its birth and its death. The following article describes the evolution of typical stars. Formation The space between stars contains gas and dust at a very low density. This interstellar matter tends to gather into clouds (see nebula). Sometimes the density becomes high enough so that gravity causes contraction, leading to the formation of a protostar. As a protostar slowly contracts, its pressure and temperature increase, the temperature rise being the result of the release of gravitational energy. Any hot object radiates energy, and the protostar eventually becomes hot enough to shine, although temperatures are not yet great enough to sustain nuclear reactions. The pressure builds up enough almost to balance gravity, but the radiation emitted drains energy and inhibits the ability of the internal pressure to complete the balance. Therefore the contraction
