B Life Cycle of a star HR Diagram

B- Life Cycle of a star HR Diagram Review

The HR (Hertzsprung-Russel) Diagram

What patterns can be seen? 1. Main Sequence: Most stars fall in this diagonal area 2. Giants: Have bright stars at the right 3. Supergiants: Have the brightest stars in the top center 4. White Dwarfs: Hot stars, but not very bright at the bottom left or bottom center

Birth of a Star • 1 st- Stars begin their lives as parts of NEBULAS- large clouds of gas and dust.

Birth of a Star cont’d • 2 nd- Gravity acts – Pulls the nebulas closer. – Increases the pressure. – Starts burning. • Creates a Prostar

3 rd- Death of a Star • Most stars burn H 2 gas and are on the main sequence. • When a star runs out of fuel (H 2), it starts to “die”. • Depending on its mass, it may either become a giant or a supergiant which burn Helium gas.

Low or Medium mass stars (1. 5 -3 times the Sun’s mass) • Low or medium mass stars become red giants. • Dying stars expand form planetary nebulae. • The remaining blue-white core is called a “White dwarf” • When the star is dead it stops glowing and becomes a black dwarf. • http: //phschool. com/atschool/phsciexp/active_ art/stellar_evolution/index. html

High mass stars (More than 3 times the Sun’s mass) • When the fuel of high mass stars run out, they quickly evolve into brilliant supergiants. • Supergiants can collapse on themselves and explode as a SUPERNOVA. • After the Supernova, gravity packs the remaining mass into a smaller space. • The gravity is so strong that even light cannot escape. This is called the Black Hole. http: //phschool. com/atschool/phsciexp/active_art/st ellar_evolution/index. html

Now • http: //sunshine. chpc. utah. edu/labs/star_ life/hr_interactive. html • Draw the diagram to show the life cycle of a star • http: //phschool. com/atschool/phsciexp/a ctive_art/stellar_evolution/index. html

The HR (Hertzsprung-Russel) Diagram