Life Cycle of Stars

• Describe the early stages of all stars, from a nebula to the main sequence.

• Explain how a star's initial mass determines its life cycle path.

• Differentiate between the life cycles of average-mass and high-mass stars.

• Define key terms like nebula, supernova, white dwarf, and black hole.

Key Vocabulary

Nebula

A vast cloud of gas and dust in space, often referred to as a star nursery.

Main Sequence

The longest stage in a star's life, during which it fuses hydrogen into helium.

Red Giant

An aging star that has run out of core hydrogen, causing it to expand and cool.

Supernova

The colossal and brilliant explosion of a massive star at the end of its life cycle.

Black Hole

A region where gravity is so intense that nothing, not even light, can escape its pull.

White Dwarf

The dense, planet-sized remnant core of a star after exhausting its nuclear fuel.

The Birth of a Star

• Stars are hot, burning spheres of gas, mostly hydrogen and helium.

• A star's life begins in a nebula, a giant cloud of gas and dust.

• Gravity pulls this material together, forming a hot, glowing core called a protostar.

• Nuclear fusion in the core marks the start of the main sequence phase.

Life Cycle of an Average-Mass Star

• An average-mass star, like our Sun, uses up its hydrogen fuel.

• ​Its outer layers expand and cool, turning it into a red giant.

• The outer layers of gas drift away, forming a planetary nebula.

• The remaining core, a white dwarf, cools to become a black dwarf.

Life Cycle of High & Extremely High Mass Stars

• Stars with more mass than the Sun have shorter, more dramatic lives.

• The star becomes a red supergiant, a very massive and luminous star.

• Its core collapses, causing a brilliant and massive explosion called a supernova.

• This can leave behind a neutron star or a light-trapping black hole.

• A star's mass determines its life cycle path and eventual fate.

• Average-mass stars, like our Sun, end their lives as a white dwarf.

• High-mass stars explode in a supernova, leaving behind a neutron star.

• The most massive stars collapse to form a black hole.