Life Cycle of Stars Nebula hundreds of light

Life Cycle of Stars • Nebula • hundreds of light years in size • contract under gravity http: //en. wikipedia. org/wiki/Image: Horsehead-Hubble. jpg

Life Cycle of Stars • Protostar • radiate heat from gravitational contraction http: //en. wikipedia. org/wiki/Image: Herbig-Haro_object_HH 32. jpg

Life Cycle of Stars • Main Sequence Stars • fuse hydrogen into helium (releases energy) • hydrostatic equilibrium • most of star’s life spent on main sequence http: //www. oswego. edu/~kanbur/a 100/images/hydrostaticequilibrium. jpg

Life Cycle of Stars • hydrogen depleted in core • core composed of helium • core contracts and heats, outer layers expand cool • star leaves main sequence http: //personal. tcu. edu/~pmarcum/courses/P 2083/handouts/starevol 1_lect. html

Life Cycle of Stars • low mass stars turn into Red Giant Stars • helium fuses into carbon • very low mass stars (<1/4 solar mass) do not fuse helium http: //fas. org/irp/imint/docs/rst/Sect 20/Arcturus. jpg

Life Cycle of Stars • helium depleted in core • core contracts and heats, outer layers expand cool • temperatures not hot enough to fuse carbon • star leaves red giant region • unstable http: //personal. tcu. edu/~pmarcum/courses/P 2083/handouts/starevol 1_lect. html

Life Cycle of Stars • Planetary Nebula • outer layers expelled into space • small, dense, hot core exposed http: //en. wikipedia. org/wiki/Image: Eskimo_nebula_%28 cropped%29. jpg

Life Cycle of Stars • White Dwarf • electron degeneracy pressure • cool over time http: //www. astronomy. ohio-state. edu/~pogge/Ast 162/Unit 3/Images/White. Dwarf. gif

Life Cycle of Stars • high mass stars • evolve quickly • turn into Supergiant Stars http: //abyss. uoregon. edu/~js/images/Aldebaran. jpg

Life Cycle of Stars • Supergiant Stars are massive enough to produce temperatures and pressure high enough to fuse heavier elements in successive stages • iron core is built up http: //en. wikipedia. org/wiki/Image: Evolved_star_fusion_shells. svg

Life Cycle of Stars • iron cannot fuse into heavier elements • iron core collapses • star explodes • known as a Supernova http: //en. wikipedia. org/wiki/Image: Crab_Nebula. jpg

Life Cycle of Stars • Neutron Stars • remnant after supernova is less than 3 solar masses • neutron degeneracy pressure • fast rotating • radiate beams of energy • known as Pulsars http: //upload. wikimedia. org/wikipedia/commons/1/1 d/Vela_Pulsar_jet. jpg

Life Cycle of Stars • Black Hole • remnant after supernova is greater than 3 solar masses • neutron degeneracy pressure is overwhelmed • light cannot escape http: //en. wikipedia. org/wiki/Image: BH_LMC. png