Stellar Evolution

Stellar evolution, "is the idea that a star is born, ages, and then dies"(Lutgens & Tarbuck. 2011). There are five stages of this evolution. Below, are brief explanations of each phase of this.

Stellar Birth:

Stellar birth is thought to be triggered by a shock wave generated by a catastrophic explosion of a nearby star. Regardless of the forces from the explosion, once it occurs, gravitational attraction will cause the clouds to contract and pull every particle toward the center, and as the cloud shrinks, gravitational energy is converted to heat energy, allowing the contracting gases to slowly heat up.

Protostar Stage:

With the passage of time, the temperature of the gaseous body rises, reaching temperatures high enough to cause it to radiate energy from the surface in the form of long-wavelength red light. The temperature is not high enough to engage in nuclear fusion therefore it is not yet a star.

Main-Sequence Stage:

During this stage, the star will have little change in size or energy output. The energy that is released from hydrogen converting into helium, keeps the gas pressure high enough to prevent gravitational collapse.

Red Giant Stage:

In this stage of stellar evolution, the usable hydrogen in the star's interior is consumed leaving behind a helium-rich core. No fusion will take place at this point.

Burnout and Death:

This is the final stage of a star. Once it has exhausted all of it's nuclear fuel, it will collapse.

There are a couple opposing forces for during stellar evolution, gravitation and gaseous pressure. Gravitation causes things to collapse, while the pressure from gaseous reactions causes the stars to expand. The birth of a star begins with gravitational collapse . The energy released in fusion provides outward pressure that prevents any further collapse. A star spends the main part of its life in this state. The future of a star depends on what happens when a star runs out of its fuel.