AST112 EXAM 2 The sun

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AST112 EXAM 2 The sun
2011-11-01 08:51:42

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  1. Measurable Properties of our Sun
    • Nearest star• Distance ~ 1 AU• Radius ~ 7 x 108 m– 100x earth radius– from distance, angularsize• Mass ~ 2 x 1030 kg– 333, 000x Earth mass– from orbits of planets• Temperature ~ 5800 K– from peak of intensity atwavelength of 500 nm
  2. Composition of our Sun
    • • Sun is gaseous-violent, bubbling up close-too hot to be solid, liquid•
    • Chemical composition- 71% Hydrogen- 27% Helium- 2% other elements(at
    • surface)
    • • Sun’s layers- more dense inside- less dense near surface
  3. Outside of the Sun
    Photosphere – visible surface- sunspots Chromosphere – layer just abovephotosphere- magnetic activityspicules Corona – extended, rarified surface
  4. Outside the surface of the SUN
    • 1. Photosphere - SunspotsGranulation
    • 2. Chromosphere - spicules
    • 3. Corona- Coronal holes- Prominences - Solar flares
    • 4. Solar Wind
    • visible surface of the SunTwo features:• sharp edge“limb”• brighter
    • incenter thanalong the limb“limb darkening”limb less denseless light
    • emitted
  6. Photosphereappears smooth, butis actually granular• Granules ~ 1000 kmacross• Convection cells ofgas rising and falling
  7. Photosphere: Sunspots
    Sunspot – magnetic features on photosphere- cooler than photosphere (DARK) ~ 3-4000 K- many 10,000 km’s across!
  8. Sunspot Cycle:•
    The number of sunspots changes daily• The location of Sunspots changes daily
  9. Sunspot Cycle:
    •  Can determine the rate of rotation of the Sunfrom the measurement of
    • Sunspot MovementGalileo was first to attempt to measure SolarRotation
    • from his daily drawings of the sunspots
  10. Sunspot Cycle: a cycle of sunspots 11 yearsThe number of sunspots reaches a peak every 11 years
  11. Sunspot Cycle:Sunspot location also changes• ~30 degrees of Sun’s equator• spots move gradually towardSun’s equator
  12. Solar Rotation –
    • varies between 25-35 days• the Sun is not asolid body like a ball•
    • different partsrotate at differentrates• equator rotatesvery rapidly: 25
    • days• poles take longer:35 days
  13. Sunspot features
    Sunspots in pairs– positive andnegativeRegions ofintensemagnetic fieldCooler: 3-4000 K
  14. Sunspot Cycle
    :Sunspot polarity also changes every ~11 years• North and South polarity reverse•total “Solar Cycle” is 22 years
  15. Chromosphere•
    Thin layer above photosphere• 2000-3000 kmthick• 10,000 K
  16. Flares
    Sudden eruptions ofenergy from SunLots of energy –billions of megatonsat a timeLots of radiation -Can be dangerousfor astronauts
  17. Solar Flares:
    Larger “eruption” in Corona“eruptions” on the Sundue to:changes in the Sun’smagnetic field
  18. Prominences
    • Gas held above sun’s surface by magnetic field• Can last minutes to months
  19. Corona:
    million degree “halo” surrounding SunVery thin andtenuousVery hotVery large –extends millionsof miles intospace
  20. Corona changes structure duringsolar cycle
  21. Coronal loops:features are related to the Sun’s magnetic field
    charged particles move with magnetic fields
  22. Layers of Sun’s atmosphere linkedto each other
    Coronal loops coming out of sunspots
  23. Coronal Mass Ejections
    Blast of gas moving out from the CoronaSpeeds as high as 1000 km/s50,000 km above the Sun’s surface
  24. Solar Wind
    :the flow of gas from the Corona into spacemoves past Earth ~4 days after it leaves SunVan Allen Belts trap charged particles
  25. Helioseismology
    The Sun “sings” and ringslike a bell