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Life cycle of the Stars

Life cycle of the Stars. Source: Dr. Jim Lochner, NASA/GSFC Presented in Tudhoe by Christos & Dave. Twinkle, Twinkle, Little Star. How I Wonder What You Are ... . Stars have D i f f e r e n t c o l o r s Which indicate different temperatures

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Life cycle of the Stars

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  1. Life cycle of the Stars Source: Dr. Jim Lochner, NASA/GSFC Presented in Tudhoe by Christos & Dave

  2. Twinkle, Twinkle, Little Star ...

  3. How I Wonder What You Are ... • Stars have • Differentcolors • Which indicate different temperatures • The hotter a star is, the faster it burns its life away.

  4. Stellar Nursery Space is filled with the stuff to make stars. http://imgsrc.hubblesite.org/hu/db/1995/44/videos/a/formats/low_mpeg.mpg

  5. Collapse to Protostar • Stars begin with slow accumulation of gas and dust. • Gravitational attraction of Clumps attracts more material. • Contraction causes Temperature and Pressure to slowly increase.

  6. Nuclear Fusion ! • At 15 million degrees Celsius in the center of the star, fusion ignites ! • 4 (1H) --> 4He + 2 e+ + 2 neutrinos + energy • Where does the energy come from ? • Mass of four 1H > Mass of one 4He E = mc2

  7. A Balancing Act • Energy released from nuclear fusion counter-acts inward force of gravity. Throughout its life, these two forces determine the stages of a star’s life.

  8. The Beginning of the End: Red Giants • After Hydrogen is exhausted in core ... • Energy released from nuclear fusion • counter-acts inward force of gravity. • Core collapses, • Kinetic energy of collapse converted into heat. • This heat expands the outer layers.

  9. A Red Giant

  10. A Red Giant You Know • Meanwhile, as core collapses, • Increasing Temperature and Pressure ...

  11. More Fusion ! • At 100 million degrees Celsius, Helium fuses: • 3 (4He) --> 12C + energy • (Be produced at an intermediate step) • (Only 7.3 MeV produced) • Energy sustains the expanded outer layers • of the Red Giant

  12. The end for solar type stars After Helium exhausted, outer layers of star expelled Planetary Nebulae http://oposite.stsci.edu/pubinfo/mpeg/OrionAnim.mpg

  13. White dwarfs • At center of Planetary Nebula lies a • White Dwarf. • Size of the Earth with Mass of the Sun “A ton per teaspoon” • Inward force of gravity balanced by repulsive force of electrons. • http://imgsrc.hubblesite.org/hu/db/2002/10/videos/b/formats/low_mpeg.mpg

  14. The End of the Line for Massive Stars • Massive stars burn a succession of elements. • Iron is the most stable element and cannot be fused further. • Instead of releasing energy, it uses energy.

  15. Supernova ! http://imgsrc.hubblesite.org/hu/db/2001/09/videos/b/formats/low_mpeg.mpg http://chandra.harvard.edu/resources/animations/sn1987a_lg.mov

  16. What’s Left After the Supernova • Neutron Star (If mass of core < 5 x Solar) • Under collapse, protons and electrons combine to form neutrons. • 10 Km across • Black Hole (If mass of core > 5 x Solar) • Not even compacted neutrons can support weight of very massive stars. http://chandra.harvard.edu/resources/animations/black_hole_sm.mov

  17. A whole new life: X-ray binaries In close binary systems, material flows from normal star to Neutron Star or Black Hole. X-rays emitted from disk of gas around Neutron Star/Black Hole. http://imgsrc.hubblesite.org/hu/db/2000/24/videos/a/formats/low_quicktime.mov

  18. Event Horizon Accretion Disk Jet (not always present) Singularity (deep in center) Black Holes - Up Close and Personal

  19. Reprise: the Life Cycle Sun-like Stars Massive Stars

  20. Materials for Life Cycles of Stars • This presentation, and other materials on the Life Cycles of Stars, are available on the Imagine the Universe! web site at: • http://imagine.gsfc.nasa.gov/docs/teachers/lifecycles/stars.html

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