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A modest G2 star, conveniently located 150,000,000 km from Earth.

The Sun. A modest G2 star, conveniently located 150,000,000 km from Earth. Solar Interior. The core is the energy source, where hydrogen fuses into helium. Heat from the core spreads out through the radiative and convective zones. How do we know...?.

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A modest G2 star, conveniently located 150,000,000 km from Earth.

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  1. The Sun A modest G2 star, conveniently located 150,000,000 km from Earth.

  2. Solar Interior The core is the energy source, where hydrogen fuses into helium. Heat from the core spreads out through the radiative and convective zones.

  3. How do we know...? Neutrinos from nuclear fusion in the Sun’s core can be detected at Earth. Sudbury Neutrino Observatory (Sky and Telescope)

  4. How do we know...? Helioseismology uses vibrations of the Sun’s surface to map its interior. NJIT

  5. Photosphere • The part we see! • Nearly all the energy from fusion is radiated into space from the photosphere. • Sunspots let us see rotation (27 days)

  6. Photosphere — Sunspots SST (Royal Swedish Academy of Sciences)

  7. SST (Royal Swedish Academy of Sciences)

  8. What are Sunspots? • Strong magnetic fields coming up from the solar interior. • The field is strong enough to inhibit convection, so the surface cools & darkens. • They last from days to weeks, then fragment and spread out.

  9. Chromosphere • Actually above the photosphere! • Seen by making images of spectral absorption lines • The structure reflects the Sun’s magnetic field.

  10. Corona (solar eclipse) • What’s this? • Sun’s outer atmosphere • Tenuous, transparent • Only one millionth as bright as photosphere.

  11. Corona in X-rays • Millions of degrees (much hotter than photosphere!) • Photosphere does not emit X-rays.

  12. Coronal loops Filamentary structure traces the magnetic field TRACE

  13. Temperatures • The power source is in the core (Temperature 15 MK). • Temperature decreases until we get to the photosphere (5800 K). • The chromosphere is hotter (up to 20,000K). • Above this is a hot corona (1-10 MK) that extends into space. • What heats the corona? • We think it’s the Sun’s magnetic field, but the process is not well understood!

  14. Corona compared to sunspots

  15. Magnetic activity comes and goes on an 11-year cycle Solar Cycle

  16. 11 year cycle Coronal activity increases with the sunspots 1995 1991

  17. Many sunspots Coronal mass ejections Flares High activity

  18. Solar Flare TRACE

  19. Aurora Australis and Borealis

  20. Earth’s magnetosphere

  21. Less x-rays produced Fewer sunspots Low activity

  22. Jupiter has a very large magnetosphere. Does it exhibit aurora? • Yes • No, its too far away • No, its not solid • Cannot conclude

  23. Compare x-ray and visible Movie

  24. Sun • Layers: • Corona • Chromosphere • Photosphere • Core • Activity cycle • Sunspots, mass ejections

  25. Sun: 1.4 million Km Mercury: 4,880 Km Venus: 12,100 Km Earth:12,756 Km Mars: 6,787 Km Jupiter: 142,800 Km Saturn: 120,600 Km Uranus: 51,300 Km Neptune: 49,100 Km You are making a mobile with a basketball for the Sun. What could you use for the other planets ?

  26. SOHO

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