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Main Sequence Lifetimes

Main Sequence Lifetimes. Time on Main Sequence How much fuel it has (Core H) How fast it consumes the fuel (Luminosity). Main Sequence Lifetimes. Main Sequence Lifetimes. Our Sun M = 1 M ( ) and L = 1 L ( ) t MS-lifetime = 10 10 years = 10 billion years

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Main Sequence Lifetimes

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  1. Main Sequence Lifetimes • Time on Main Sequence • How much fuel it has (Core H) • How fast it consumes the fuel (Luminosity)

  2. Main Sequence Lifetimes

  3. Main Sequence Lifetimes • Our Sun M = 1 M() and L = 1 L() • tMS-lifetime = 1010 years = 10 billion years • Large Mass Bright Star M = 10 M() and L = 105 L () • tMS-lifetime = 1010 • tMS-lifetime = 106 years = 1 Million years

  4. Nuclear Fusion and Forces of Repulsion • For Hydrogen repulsion of 2 (1+) charges • At 1 Atomic radius Frepulsion= 2.3 x 10-8 N • For Helium repulsion of 2 (2+) charges • At 1 Atomic radius Frepulsion= 9.2 x 10-8 N • Ratio of forces 9.2/2.3~4x • For Hydrogen, we had 2 pairs of H fused to make 1 Helium. • For Helium, we need 3 pairs of He to fuse to make 1 Carbon  so ratio 3/2(4) = 6x  6x as much force

  5. Nuclear Fusion • Hydrogen Fusion requires temps ~ 7 Million K • Helium Fusion requires temps ~ 100 Million K • A bit more than 6x (~14x) • Energy from Helium fusion ~0.1 Energy released in Hydrogen fusion • All stars > 0.5 M() can create Helium burning Temps of 100 million K

  6. Nuclear Fusion • High Mass Stars create 100 Million K by contracting Core a little. • Low Mass Stars create 100 Million K by contracting Core a lot! • If a Low Mass Star contracts Core a lot, Core can become Degenerate!!

  7. Degenerate States of Matter • Normal Matter only one atom may exist in a particular energy state. This causes atoms to have some spatial separation. • Degenerate Matter many atoms may exist in the same energy state. This causes atoms to become quite close together.

  8. Degenerate Matter • Super-Fluids • Super-Conductors • Bose-Einstein Condensates

  9. Super-Fluid http://london.ucdavis.edu/~zieve/Research/creep.jpg

  10. Super-Conductor http://sci-toys.com/scitoys/scitoys/magnets/levitation_closeup.jpg

  11. Bose-Einstein Condensates http://math.nist.gov/mcsd/savg/vis/bec/3D.00007.jpg

  12. Bose-Einstein Condensates • http://science.nasa.gov/headlines/y2002/images/neutronstars/magnetar_huge.jpg

  13. Degenerate Core of a Star • Gas atoms so close act like Solid! • Heat a Gas, Changes in Both Volume and Pressure • Heat a Solid, Small Changes in both Volume and Pressure.

  14. High Mass Star (Normal Gas Core) • Fusion releases Energy  Heats Gas • Heated Gas  Gas Expands due to increase Pressure • Expanded Gas  Cools Gas • Cooling Gas decreases Nuclear Fusion rate • Decreased Nuclear Fusion Rate  Pressure drops • Gas Contracts  Increased Temps  Increased Fusion • Gas properties regulate Nuclear Fusion

  15. Low Mass Star (Degenerate Core) • Fusion releases Energy  Heats Gas (Solid) • Heated Solid  No Increase in Pressure • No Increase in Pressure  No Expansion • No Expansion  No Cooling • Increased Temperatures  Increased Nuclear Rate • Increase Nuclear Rate  Increased Release of Energy • Increased Temps etc…… • No Regulation of Nuclear Fusion  Helium Flash!!

  16. Helium Flash • Explosive release of energy • Usually restores Degenerate Core back to normal Core • Helium Flash Ends First Red Giant Phase of Low Mass Stars and start Yellow Giant Phase • High Mass Stars do not have a helium flash • High Mass Stars go originally to Yellow Giant Phase and then expand into Red Giants • Onset of Helium Burning often cause stars to become unstable (Variable Stars)

  17. Lagrange Points http://www.jwst.nasa.gov/orbit.html

  18. Mass Mystery??? • Both stars in a binary form about same time • More massive stars evolve faster • Red Giant star (on left) is less massive than Main Sequence star (on right) • Solution Mass Transfer!!!

  19. More Massive Star is Dimmer?? • Β Lyrae • More Massive Star is Dimmer • Solution – Accretian Disk blocks some of light!!

  20. Stellar Evolution in a Globular Cluster In the old globular cluster M55, stars with masses less than about 0.8 M are still on the main sequence, converting hydrogen into helium in their cores. Slightly more massive stars have consumed their core hydrogen and are ascending the red-giant branch; even more massive stars have begun helium core fusion and are found on the horizontal branch. The most massive stars (which still have less than 4 M ) have consumed all the helium in their cores and are ascending the asymptotic giant branch.

  21. Dredges • 1rst – After Core H ceases • Relative abundance of Carbon, Nitrogen and Oxygen changed at surface • 2nd – After Core He ceases • Again Relative abundance of C, N, and O changed • 3rd – After during AGB (if M > 2 M() ) • Prominent Carbon compounds. C2, CH, CN • Strong C absorption lines in spectra • Carbon Star!!

  22. TT Cygni is an AGB star in the constellation Cygnus that ejects some of its carbon-rich outer layers into space. Some of the ejected carbon combines with oxygen to form molecules of carbon monoxide (CO), whose emissions can be detected with a radio telescope. This radio image shows the CO emissions from a shell of material that TT Cygni ejected some 7000 years ago. Over that time, the shell has expanded to a diameter of about ½ light-year.

  23. Later Stage of Low Mass Stars • Helium Shell burning decreases as its fuel is used up • Dormant Helium Shell provides insufficient pressure to support Dormant Hydrogen Shell • Hydrogen Shell contracts, Heats up, Re-ignites! • Helium produced in Hydrogen Shell adds to Helium Shell Fuel • Hydrogen Burning re-heats Helium Shell, Small Helium Flash!! • Helium Shell Burning Pushes Star out again • Outer layers detach!! Planetary Nebula!!

  24. Planetary Nebulae • Thermal Pulses happen in increasingly shorter intervals over time • 1 M() loses about 40% of its mass this way • As outer layers are ejected, hot core exposed • Core Temp ~ 100,000 K emits UV radiation • Radiation ionizes gas creating Fluorescence glows • Radiation also propels gas outward in increasingly larger rings • Non-symmetric radiation creates hour-glass shapes

  25. 1980’s • Two “Neutrino Telescopes” went into operation • Kamiokande (U-Tokyo and U-Penn) detector in a zinc mine in Japan • IMB (U-Cal at Irvine, U-Michigan, and Brookhaven) detector in a salt mine in Ohio • Neutrinos interacts with a proton in the water creating a supersonic positron • Positron moves faster than the speed of light in water creating a shockwave effect known as Cerenkov radiation

  26. http://ncas.sawco.com/condon/text/s6c06f1b.htm

  27. http://www.pbs.org/wgbh/nova/barrier/boom/images/cone.jpeg

  28. http://www.sonicbooms.org/T38/T38c3.jpg

  29. http://www.simulationinformation.com/sonic%20boom.jpg

  30. http://www.anomalies-unlimited.com/Odd%20Pics3/Images/shuttlesonic.jpghttp://www.anomalies-unlimited.com/Odd%20Pics3/Images/shuttlesonic.jpg

  31. http://www.physlink.com/Education/AskExperts/ae219.cfm

  32. http://dept.physics.upenn.edu/balloon/cerenkov_radiation.htmlhttp://dept.physics.upenn.edu/balloon/cerenkov_radiation.html

  33. http://www.physlink.com/Education/AskExperts/ae219.cfm

  34. Solar Neutrinos Vs Supernova Neutrinos?? • Energy • Solar Neutrinos ~<1 MeV • Supernova Neutrinos ~>20 MeV • Measuring Properties of Cerenkov radiation, the speed of the e+ which created the radiation can be found • Speed of e+ gives originally energy of neutrino which collided with proton that created the e+

  35. February 23, 1987 • 12 second burst of neutrinos detected • Kamiokande detected 11 Neutrinos • IMB detected 8 Neutrinos • The Earth was subjected to a neutrino flux of approximately 1016 neutrinos • Supernova emitted 1058 neutrinos in about 10 seconds 160,000 years ago • Approximately 100x the Energy the Sun has emitted in its entire lifetime!! • About 100x the amount of light energy the Supernova emitted • Approximately 10x the total luminosity of the stars in the entire observable universe at the moment

  36. February 23, 1987 • 3 hours later Light arrived from Supernova 1987 ???? • Neutrinos not blocked by gas layers of the star • Light created only after shockwave reached the outer-most layers of the star

  37. Why was SN 1987A Unusual? • Peak Intensity about 0.1 of intensity of other observed Supernovas • Confusion over whether progenitor star was a Red Supergiant or a B3 I Blue Supergiant? • Pop I or Pop II star? • Possible Pop II meaning it oscillated between Red and Blue Supergiant.

  38. Supernova 1987A • In Blue Supergiant phase, radius is about .1 of size than when in Red Supergiant phase • When explosion occurred more mass closer to core, more energy needed to push outer layers away, less available for creating brighter light • Type II Supernova *****

  39. Types of Supernovas • Type II do have prominent Hydrogen Lines • Type I do not have prominent Hydrogen Lines in their spectra • Type I further subdivided into • Type Ia which has strong absorption lines of Si • Type Ib which does not have Si but does have absorption lines of He • Type Ic which has neither

  40. http://csep10.phys.utk.edu/guidry/violence/sn87a-rings.html *****

  41. http://apod.nasa.gov/apod/image/0402/sn1987a_acsHubble_full.jpghttp://apod.nasa.gov/apod/image/0402/sn1987a_acsHubble_full.jpg *****

  42. http://physics.uoregon.edu/~courses/BrauImages/Chap21/FG21_08A.jpghttp://physics.uoregon.edu/~courses/BrauImages/Chap21/FG21_08A.jpg

  43. Type II, Ib, Ic are found near sites of new star formation. • Type Ia found in galaxies where there are no ongoing star formations

  44. Supernova leftovers • Remnants • Gasses and elements • Core Relics • Neutron Stars • Black Holes

  45. Why More Supernovas in other Galaxies?? • Ought to see about 5 per century based on what we see in other galaxies (~100 remnants seen with radio in other galaxies) • Last Supernova in our Galaxy 1604 – Kepler • 1572 Brahe • 1054 China • Interstellar dust blocks best star forming regions from our view

  46. Neutrons form : • Supernova’s Create many reactions • Neutrons first discovered in 1932 Chadwick • Zwicky (Caltech) and Baade (Mt. Wilson Obs) Proposed parallel to White Dwarf, Neutron Star • White Dwarf uses Degenerate e- pressure to sustain outer layers weight • Neutron Star uses Degenerate n pressure • Neutrons can with stand more force, hence 1.4 M() limit no longer applies

  47. Improbabilities for a Neutron Star • Thimbleful would weigh 100 million tons Density 1017 kg/m3 • Recall 1 teaspoon of White Dwarf weighs ~ 5.5 tons!! Density 109 kg/m3  1 M() White Dwarf would have a diameter of 10,000 – 12,000 km, Size of Earth!!  1 M() Neutron Star would have a diameter of 30 km (19 miles), Size of large city!!

  48. http://www.astro.umd.edu/~miller/nstar.html

  49. 1960’s Cambridge England • 1967 Anthony Hewish’s Research Group from Cambridge University finish 4 ½ acre radio telescope array • Jocelyn Bell, Graduate Student, discovers regular pulses of radio noise from one location in the sky. • Period of Pulses was 1.3373011 seconds

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