Earth and Space Unit 2 Life Cycle of a Star

Nebula

A huge cloud of gas and dust. Gravity force begins to clump gas/dust. Huge amounts of hydrogen.

Protostar

Gravity pulls atoms even closer together. Fusion begins and the star ignites, giving off heat and light.

Main Sequence

Main stage of a star’s life where it spends most of its life. Balance between thermal pressure (outward) and gravity (inward) is key.

Red Giant/Supergiant

Hydrogen (fuel) is depleted, so helium begins to fuse. Energy output increases, so the outer layers are pushed outward.

White Dwarf (low mass stars)

Fusion stops at carbon and gravity “wins.” The core collapses to create it. The outer layers are pushed out, creating a new planetary cloud/nebula.

Supernova (high/highest mass stars)

Fusion stops at iron. Huge amounts of gravity cause the outer layers to bounce off the core in a giant explosion (creating elements heavier than iron).

Neutron star (high mass stars)

Gravity compresses the core. there is so much density that protons and electrons collide and become neutrons.

Black hole (highest mass stars)

There is so much density that protons and electrons collide but keep going. Gravity is so powerful that not even light can escape.

Forming nebula (high/highest mass stars)

The outer layer material ejected from the supernova slows down and becomes a new nebula cloud… and so the cycle continues.

Star mass

High mass: Blue/white in color, shorter lifespan, will end as a neutron star/black hole

Low mass: Reddish in color, longer lifespan, will end as a white dwarf