A Star is Born

1. A Star is Born Photo in 1995 of the Orion Nebula.

2. energy …produce their energy via nuclear fusion in their cores …lifestyles are determined by the struggle for equilibriumbetween gravity and pressure mass …are massive, hot, glowing balls of gas Stars….

3. Star Nurseries … nebula – interstellar cloud of gas and dust a star is born in the Orion Nebula Hayden Planetarium, American Museum of Natural History http://haydenplanetarium.org/movies/ava/S0801starform.mpg

4. A star is born… From collapsing cold clouds of interstellar gas and dust… clouds rotate as they collapse … conserving angular momentum … forming the smaller clumps that will become stars Orion Nebula

5. Birth of a Star: Nebula Black Widow Nebula

6. Birth of a Star: Nebula Crab Nebula

7. Birth of a Star: Nebula Bow Shock: Named for the crescent-shaped wave made by a ship as it moves through the water, a bow shock can be created in space where two streams of gas collide.

8. Birth of a Star: Nebula Bok globules or Thackeray's Globules are dark clouds of dense cosmic dust and gas in which star formation sometimes takes place.

9. High Mass Stars Bright Burn “fuel” rapidly (hundreds of millions of years) Have very short lives Example: Rigel in the Orion Constellation A star’s initial mass determines its life • Low Mass Stars • Less bright • “Burn” for billions of years • Have very long lives • Examples: Sun, brown dwarfs

10. Life Cycles of Stars Stars and Galaxies A star’s fate depends on its mass. A star with a mass similar to the sun’s will become a white dwarf.

11. Life Cycles of Stars Stars and Galaxies A star with a mass eight or more times greater than the sun’s will either become a black hole or a neutron star.

14. Life Cycles of Stars The Hertzsprung-Russell diagram plots a star’s luminosity against its surface temperature. The diagram’s groups of stars represent life-cycle stages of stars. Most stars are main-sequence stars. Red Supergiants Blue Supergiants Highest <Main Sequence> Red Giants Luminosity White Dwarfs Red Dwarfs Lowest Hertzsprung-Russell diagram Temperature Hottest Coolest Stars and Galaxies VOCABULARY main sequence giant star supergiants white dwarf nebula planetary nebula supernova neutron star pulsar black hole

15. Hertzsprung-Russell Diagram: • Ejmar Hertzsprung (1873-1967) – Copenhagen – Began his career as a Chemical Engineer. While working and independently at the same time… • Henry Norris Russell (1877-1957) – Princeton – Student then professor. • A graph that separates the effects of temperature and surface area on stellar luminosities. • The HR Diagram is much like the same thing as producing a graph of people’s height vs. weight.

16. Hertzsprung-Russell diagram • Parts of an H-R diagram • Main-sequence stars • 90% of all stars • Band through the center of the H-R diagram • Sun is in the main-sequence • Giants (or red giants) • Very luminous • Large • Upper-right on the H-R diagram

17. Hertzsprung-Russell diagram • Parts of an H-R diagram • Giants (or red giants) • Very large giants are called supergiants • Only a few percent of all stars • White dwarfs • Fainter than main-sequence stars • Small (approximate the size of Earth) • Lower-central area on the H-R diagram • Not all are white in color • Perhaps 10% of all stars

18. Hertzsprung-Russell diagram