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Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
Astrophysics HL
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Astrophysics HL

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IBO Diploma Physics Option E

IBO Diploma Physics Option E

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  • 1. Astro - HL
  • 2. Star Formation
    • Dark Nebula -Birthplace of Stars
      • Example- Horsehead Nebula
        • In the constellation Orion.
        • The birthplace of stars
        • 75% Hydrogen, 24% Helium, 1% dust (many different elements)
  • 3. Star Formation
    • Gravity begins to pull the gas and dust together.
    • They lose gravitational potential energy…this is converted into kinetic energy.
    • The temperature increases.
  • 4.  
  • 5. The Perfect Storm
    • A small region in the Swan Nebula, 5,500 ly away, described as 'a bubbly ocean of hydrogen and small amounts of oxygen, sulphur and other elements'.
  • 6. Ant Nebula
    • Name is Mz3, lies within our galaxy between 3,000 and 6,000 ly from Earth.
  • 7. Cone Nebula
    • 2.5 light years in length (the equivalent of 23 million return trips to the Moon)
  • 8. Hour Glass Nebula
    • 8,000 light years away, has a "pinched-in-the-middle" look because the winds that shape it are weaker at the centre.
  • 9. Star Formation
    • Protostar
      • High temperature leads to ionisation of elements.
      • E-M energy is emitted.
      • The star can have considerable Luminosity.
      • 5000 times the surface area and 100 times as Luminous as our Sun.
  • 10. Star Formation
    • Protostar-
      • Temperature continues to increase…
      • Electrons stripped from the atoms in the core.
      • A plasma is formed.
  • 11. Star Formation
    • Main Sequence Star-
      • Nuclear Fusion starts up.
      • Temperatures now high enough to fuse Hydrogen into Helium.
      • Gravitational contraction will now stop as the Fusion process will offset the contraction.
      • “ Hydrostatic Equilibrium”
  • 12. You are not Required to Memorize these Reactions
  • 13. Main Sequence Stars
    • Where a star lands on the Main Sequence depends on its mass.
    • A star will
    • stay at this
    • place on the
    • main sequence
    • for its lifetime
    • as a Main Sequence
    • Star.
  • 14. Main Sequence Stars
    • The life of a Main Sequence star is determined by its mass.
    • High Mass =
    • Short Lifespan.
    • Sun (1M) - 10 Billion
    • Years.
    • 15 M - 10,000
    • Years.
  • 15. Main Sequence Stars
    • Once hydrostatic equilibrium is reached… the star will remain stable for as long as it is a Main Sequence Star (thousands to up to billions of years).
  • 16. The Future of our Sun
    • There is enough Hydrogen in our Sun’s core to produce fusion for another 5 billion years.
    • Eventually the core will be mostly Helium.
    • Hydrogen Fusion will then begin outside the core.
  • 17. The Future of our Sun
    • No fusion happening in the core to counteract the gravitational contraction.
    • The core will begin to collapse.
    • This raises the cores temperature.
    • Sun will start to expand.
    • Surface temperature will drop.
    • Sun enters RED GIANT STAGE.
  • 18. The Future of our Sun
    • Luminosity increases due to massive size.
    • Out to the orbit of Venus.
    • Core temperature now so high that Helium can be fused.
      • Higher temperature required to fuse Helium as it has two positive charges.
  • 19. The Future of our Sun
    • Helium fused into Carbon and Oxygen.
      • This is where our carbon comes from.
      • Once the Helium is used up in the core, the star collapses due to the high mass core even more… this raises the temperature even higher!
      • Burning of Hydrogen in the outer layers causes further expansion.
  • 20. The Future of our Sun
    • At this point the Sun’s surface will reach out to the Earth’s Orbit!
    • 10,000 times as luminous as today.
    • The sun will start to shed layers… these layers are called planetary nebula.
  • 21. The Future of our Sun
    • The core will now be exposed.
    • The core is called a White Dwarf.
      • About the size of the Earth.
      • Very hot, very small.
      • Not luminous.
      • Will eventually cool into a cold, “dead” star called a brown dwarf.
  • 22.  
  • 23.  
  • 24.  
  • 25.  
  • 26. The Future of our Sun
    • Our Sun will eventually make Hydrogen, Helium, Carbon and Oxygen.
    • The production of these new elements from Hydrogen is called Nucleosynthesis .
  • 27. Mass – Luminosity Relationship
    • There is a relationship between the luminosity of a star and its mass
    •   L = M 3.5
    •   Where L is luminosity, M is mass in solar units and applies to all main sequence stars
    • The power (3.5) can be any value between 3 and 4 as it is itself mass dependant. 
  • 28. The Chandrasekhar Limit
    • If the initial solar mass of a star is greater than 8 solar masses… then the star will become a…
      • Supergiant Star and eventually collapse to a…
      • Neutron Star or a Black Hole.
  • 29. The Chandrasekhar Limit
    • A star greater than 8 solar masses (1 solar mass is the mass of our Sun)… will collapse to a core…
      • With a mass of greater than 1.4 Solar Masses.
      • A neutron star or a black hole
      • If the core is less than 1.4 solar masses the star will become a White Dwarf.
  • 30. The Chandrasekhar Limit
    • This 1.4 solar mass of the core boundary is called the Chandrasekhar limit.
      • Famous Indian astronomer.
      • Less than 1.4 solar mass for the core… electron degeneracy prevents further collapse.
        • Electrons cannot be packed together any further.
  • 31. THE OPPENHEIMER-VOLKOFF LIMIT
    • is the equivalent to Chandrasekhar but applies to neutron stars.
  • 32. The Supergiants
    • Stars with masses greater than 8 solar masses initially will evolve into a Supergiant star…
      • Eventually collapse to a core greater than 1.4 solar masses.
        • Become a Neutron Star or a Black Hole.
  • 33. The Supergiants
    • The star will undergo the same process as a Red Giant…
      • Fusion of Helium in the inner core.
      • Fusion of Hydrogen in the outer layers.
      • Expansion.
      • Cooling at the surface of the star.
      • Subsequent fusion of Oxygen and Carbon in the core.
  • 34. The Supergiants
    • The difference is that the star is massive enough to continue to…
      • Collapse after the Oxygen and Carbon fusion.
      • Further gravitational collapse leads to further temperature rises.
      • Capable of beginning the fusion of silicon.
  • 35. The Supergiants
  • 36. The Supergiants
    • The fusion of silicon makes iron.
    • Supergiants are the brightest stars visible due to their enormous size.
    • Betelgeuse in the constellation Orion.
  • 37. The Supergiants
    • Iron cannot undergo fusion due to its very high coulombic repulsion (26 protons).
    • It would need astronomical temperatures.
    • The star has reached a critical state.
  • 38. The Supergiants
    • The star will once again begin to collapse into the core.
    • But no more fusion will take place to counteract the gravitational collapse.
    • Incredibly high temperatures lead to the combining of electrons and protons.
  • 39. The Supergiants
    • Neutrons and neutrinos are formed in large quantities.
    • High energy neutrinos form an outward pressure wave.
    • This wave hurtles outward.
  • 40. The Supergiants
    • This shock wave rips the outer layers off of the star.
    • The inner core is now exposed.
    • Huge amount of radiation floods into space.
  • 41. Supernova
    • The star has become a Supernova.
    • The luminosity for a brief moment is greater than the whole luminosity of a galaxy (1 billion stars)!
    • 96% of the stars mass is lost to space.
  • 42. Supernova
    • The explosion has enough energy to fuse all of the elements with atomic number greater than iron.
    • The gas and dust flung into space will form a dark nebula .
    • The star cycle is ready to begin again.
  • 43. Eskimo Nebula
    • NGC 2392, a ring of comet-shaped objects flying away from a dying star.  Eskimo is 5,000 ly from Earth.
  • 44. Cats Eye Nebula
  • 45.  
  • 46.  
  • 47.  
  • 48.  
  • 49.  
  • 50.  
  • 51. Neutron Stars
    • The combination of protons and electrons due to the enormous temperatures produce a neutron core.
    • A Neutron Star has been formed.
    • Very small, radius of less than 30 km! Extremely dense.
    • Oppenheimer-Volkoff Limit- upper limit for the mass of a neutron star beyond which it must collapse to become a black hole . Its value is not known exactly because the properties of neutron degenerate matter can only be estimated, but it is generally thought to be about 2 or 3 solar masses.
  • 52.  
  • 53. Mass-Luminosity relation
    • There is a relationship between the luminosity of a star and its mass
    • L = M 3.5
    • Where L is luminosity, M is mass in solar units and applies to all main sequence stars
    • The power (3.5) can be any value between 3 and 4 as it is itself mass dependant.
  • 54. Pulsars
    • A Pulsar is a Neutron Star that is rotating very rapidly.
    • Can rotate once every 2 seconds!
    • Pulsars have a large magnetic field.
    • This produces radio waves.
    • These radio waves are emitted in bursts as the star rotates.
  • 55.  
  • 56. Quasars
    • Incredibly luminous objects found in our most distant galaxies.
    • 12 Billion light years away.
    • Embryonic galaxies.
    • 10,000 times brighter than our Milky Way Galaxy.
    • Radio wave emission.
    • Very large redshifts due to their enormous distance from Earth.
  • 57.  
  • 58. Black Holes
    • Black Hole - a neutron star so dense that…
      • Gravitational Forces are enormous.
      • Even light cannot escape its gravitational pull.
      • We therefore cannot see a Black Hole!
  • 59. Black Holes
    • Light near a Black Hole will be bent.
    • Close to a Black Hole, the light bends back on itself.
    • Relativity tells us that time will cease at this point. The Event Horizon.
    • More on this in the Relativity Option.
  • 60. Black Holes
    • Evidence for Black Holes…
      • Some stars have their gases being pulled away funnel like into space…
        • Being pulled into a “Binary Star” that is a Black Hole.
  • 61. Cygnus X-1 Black Hole
    • 15 times the mass of the Sun in orbit with a massive blue companion star.
  • 62. Life Cycle Summary
    • From Chandra X-Ray Observatory
  • 63. Galaxies
    • Our Milky Way Galaxy is a Spiral Galaxy.
      • All spiral galaxies have a central bulge, a thin disc and a halo.
  • 64.  
  • 65.  
  • 66. Sombrero Galaxy
    • 28 million ly from Earth. Officially called M104, it has 800 billion suns and is 50,000 light years across.
  • 67. Galaxies
    • The central bulge
      • Greatest density of stars
      • Youngest stars
  • 68. Halo - Made up of globular clusters. Very old stars. Up to 12 Billion years old.
  • 69. Galaxies
    • Types of Galaxies …
      • Spiral
      • Elliptical
      • Irregular
  • 70.  
  • 71. Spiral Galaxies
    • Consist of a rotating disk of stars and
    • interstellar medium, along with
    • a central bulge of generally older stars.
    • Extending outward from the bulge are relatively bright arms.
  • 72. Elliptical Galaxies
    • They range in shape from
      • nearly spherical to
      • highly flattened ellipsoids and
      • in size from hundreds of millions to over one trillion stars.
    • In the outer regions, many stars are grouped into globular clusters.
  • 73. Irregular Galaxies
    • Have no specific structure.
    • The Large and Small Magellanic Clouds, the nearest galaxies to us,
      • are an example of irregular galaxies.
  • 74. Galaxies
    • All galaxies must rotate, otherwise they would collapse due to gravitational attraction.
  • 75. Galactic Clusters
    • A Galactic Cluster is a system of galaxies containing several to a thousands of members.
    • They all reside in the same area.
    • Clusters can be grouped into Superclusters .
  • 76.  
  • 77. Two Galaxies Colliding
    • 114 million ly away are two merging galaxies, NGC 2207 & IC 2163 in the distant Canis Major constellation.
  • 78. Galactic Motion
    • We learned earlier that most Galaxies are moving away from each other.
    • Expansion of the Universe.
    • Evidence- Red Shift of stellar spectra.
      • Further away… greater the Red Shift.
  • 79. Galactic Motion
    • A method of determining the recessional speed of a galaxy away from Earth is determined using the equation…
    • Where  = the difference between the spectral line from a stationary source and the spectral line from the receding galaxy.
    •  = spectral line of the stationary source.
  • 80. Example
    • A characteristic absorption line often seen in stars is due to ionized helium. It occurs at 468.6 nm. If the spectrum of a star has this line at a measured wavelength of 499.3 nm, what is the recession speed of the star?
  • 81. Solution
  • 82. Hubble’s Red Shift Law
    • We have just seen how we can determine a galaxies recessional velocity from its Redshift.
    • We can also determine the galaxies distance.
  • 83. Hubble’s Red Shift Law
    • Hubble discovered a relationship between a galaxies distance and its recessional velocity.
  • 84. Hubble’s Red Shift Law
    • Distant galaxies were receeding very fast.
    • This fits with the expanding Universe Theory.
  • 85. Hubble’s Red Shift Law
    • v ≈ d
    • v = H d
    • Where H is
    • Hubbles
    • Constant
    • It is the
    • slope of the graph.
  • 86. Hubble’s Red Shift Law
    • Hubble’s Constant is estimated to be around 65 km s -1 Mpc -1
      • Much debate on the accuracy of this value.
    • Try this Raisin Bread analogy animation
  • 87. The Big Bang
    • You are required to know the basic theory behind the stages of development of the Universe.
    • Detailed accounts are not necessary.
    • Just a general explanation.
  • 88. The Big Bang
    • At the start, the Universe would have been very hot.
    • As it expanded, the Universe cooled to a temperature where atoms could be formed.
  • 89.  
  • 90.  

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