1. The Sun

2. Basic Solar Properties Diameter (photosphere) 1,391,980 km Mass1.99 x 10 33 g Rotation Period 25 days (equator) Surface Temperature 5,800 K (effective) Spectral Class G2 V Apparent Visual Magnitude - 26.7 Absolute Visual Magnitude + 4.8 Mean Distance (Earth) 149,597,892 km

4. Solar Elemental Abundances ElementNumber % Mass % Hydrogen92.073.4 Helium7.825.0 Carbon0.020.20 Nitrogen0.0080.09 Oxygen0.060.8 Neon0.010.16 Magnesium0.0030.06 Silicon0.0040.09 Sulfur0.0020.05 Iron0.0030.14

5. 1.The core is the hot, dense central region in which the nuclear reactions that power the Sun take place. It comprises about 25% of the interior radius. 2.The radiative zone is comprised of the interior from about 25% to 85% of the solar radius. It is called the radiative zone because here (and in the core) the primary transport of energy is by photons (electromagnetic radiation). 3.The convective zone starts at about 85% of the solar radius and extends to just below the surface. It is a region in which the change in temperature with increasing radius is so rapid that the Sun becomes unstable to convection (rapid up and down motion of large packets of gas), much as the Earth's atmosphere becomes convectively unstable on a hot Summer day and produces thunderstorms.

6. Core T~ 15,000,000 - 8,000,000 Radiative T~ 8,000,000 - 500,000 ConvectiveT~ 500,000 - 10,000

7. Atmospheres Photosphere T=5800K Chromosphere T=10,000K CoronaT=2,000,000K

8. The Sun at X-Ray wavelengths

9. The Sun at UV wavelengths

10. Granulation near sunspot group The photosphere under close observation exhibits a mottled appearance that is called granulation. This is a consequence of heat convection below the photosphere.

11. The Chromosphere of the Sun The chromosphere contains spikes of gas called spicules that rise through it. This image is a superposition of 11 limb images taken at different wavelengths. Spicules are short-lived phenomena, corresponding to rising jets of gas that move upward at about 30km/sec and last only about 10 minutes.

12. The solar corona The extended outer atmosphere of the Sun is called the corona. It has a temperature of millions of degrees, but it is 10 billion times less dense than the atmosphere of the Earth at sea level.

13. The 11-Year Sunspot Cycle

14. The 22 Year Magnetic Cycle Black denotes a negative polarity (magnetic field pointing into the Sun) while white denotes a positive polarity (magnetic field pointing out of the Sun). 1.

15. Prominence on the solar limb

17. Solar Flares

18. The Zeeman Effect

19. Main branch of the proton- proton chain

20. The main branch of the PP chain consists of the following reactions: 1.Two mass-1 isotopes of hydrogen undergo a simultaneous fusion and beta decay to produce a positron, a neutrino, and a mass-2 isotope of hydrogen (deuterium). 2.The deuterium reacts with another mass-1 isotope of hydrogen to produce Helium-3 and a gamma-ray. 3.Two helium-3 isotopes produced in separate implementations of steps (1) and (2) fuse to form a Helium-4 nucleus plus two protons. The net effect is to convert hydrogen to helium, with the energy released going into the particles and gamma-rays produced at each step of the sequence.