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

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

Star Nurseries … nebula – interstellar cloud of gas and dust a star is born in the Orion Nebula Hayden Planetarium, American Museum of Natural History

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

Birth of a Star: Nebula Black Widow Nebula

Birth of a Star: Nebula Crab Nebula

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.

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.

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

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

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

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. VOCABULARY Life Cycles of Stars Stars and Galaxies Hertzsprung- Russell diagram Temperature Luminosity HottestCoolest Highes t Lowest Blue Supergiants Red Supergiants Red Giants Red Dwarfs White Dwarfs main sequence giant star supergiants white dwarf nebula planetary nebula supernova neutron star pulsar black hole

Hertzsprung-Russell Diagram: – Ejmar Hertzsprung ( ) – Copenhagen – Began his career as a Chemical Engineer. While working and independently at the same time… – Henry Norris Russell ( ) – 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.

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

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

Hertzsprung-Russell diagram