Star Formation and Evolution

Star Formation

Stars form from clouds of gas and dust called nebulae. Gravity causes these clouds to collapse, forming a protostar. As material falls inward, it heats up. When the core reaches about 10 million K, nuclear fusion ignites, and a star is born.

Main Sequence

Stars spend most of their lives on the Main Sequence, fusing hydrogen into helium in their cores. A star's mass determines its Main Sequence lifetime:

• Massive stars (10+ solar masses) - Burn hot and fast, lasting only millions of years.
• Sun-like stars - Last about 10 billion years.
• Low-mass red dwarfs - Can last trillions of years.

Post-Main Sequence Evolution

• Low-mass stars become red giants, then shed their outer layers as planetary nebulae, leaving behind white dwarfs.
• Massive stars become red supergiants, then explode as supernovae, leaving neutron stars or black holes.

Stellar Nucleosynthesis

Stars create heavier elements through fusion. Our bodies contain atoms forged in ancient stars - we are literally made of "star stuff".