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Transcript
THE LIFE CYCLE OF STARS Chapter 15 – 2 Part 1 TYPES OF STARS • A star can be classified as one type of star early in its life, and as a different type of star as it gets older. • A star is classified differently as its properties change. The Life Cycle of Sun-like Stars • Like all natural cycles, the stages in a star’s life progress from birth to death. Nebula or Protostars • A star begins life as a ball of gas and dust. • Gravity pulls the materials into a sphere. • As the sphere gets denser, the temperature rises to 10,000,000* C. • Nuclear fusion occurs as hydrogen combines into helium. Main-Sequence Stars • After a sun-like star forms, it enters the main-sequence. • This is the second and longest stage of its life. • Energy is generated in the core and causes the star to shine. • The size of the star changes very little as long as its supply of hydrogen nuclei fuse into helium nuclei. Nuclear Fusion Giants and Supergiants • When a main sequence star uses all its hydrogen in its core, helium begins to fuse. • The center then begins to shrink, and the atmosphere grows very large and cools. ANTARES White Dwarfs SIRIUS • A white dwarf is a small, hot, and dim star that is the leftover center of a red giant. • It slowly cools and becomes smaller, but can shine for a billion years. LET’S TRY IT! • ACTIVITY: THE LIFE CYCLE OF STARS