1. THE SUN Hydrostatic equilibrium

2. The source of the sun’s energy is NUCLEAR FUSION H + H → He

3. In this process… A small amount of (nuclear) mass is converted to energy.

4. Proton-proton chain

5. A neutrino Is a small, nearly mass-less fundamental particle. 65 billion neutrinos penetrate every square centimeter of the earth per second.

6. A positron Is the antimatter parallel to an electron. Antimatter is a theoretical construct that suggests there are “opposites” for the fundamental particles of physics.

7. Specifically, gamma rays High energy, short wavelength

8. When a gamma ray photon collides with an H or He nucleus It is ABSORBED then RE-EMITTED

9. As this happens over and over, The photon eventually photon loses some of its energy and changes to a different form of E- M energy. (The nuclei of atoms can absorb energy (from a gamma ray or a neutron, for instance), which produces an unstable nucleus which can then go to a lower energy by emitting a gamma ray, or by splitting (fission) in the case of a few atoms.)

10. By the time it reaches the surface which may take 15 million years) it may have been converted to….

11. Visible light…. Longer wavelength, lower frequency

12. WHY SO LONG? The sun’s great mass/gravity squeeze the gas below the surface so the particles are very close together.

13. According to Gay-Lussac’sLaw TEMEPERATURE AND PRESSURE ARE DIRECTLY RELATED SO….

14. Gay-Lussac’s Law

15. More squeezing, the gas gets hotter The hotter the gas gets, the more it wants to spread out

16. If it can’t spread out The pressure increases.

17. More pressure, more higher temperature-- The sun’s core has a high temperature—15 million Kelvins

18. The higher the temperature The greater the gas pressure pushing OUT from the core.

19. It is this pressure THAT BALANCES THE GRAVITY OF THE SUN

20. THE BALANCE BETWEEN GAS PRESSURE AND GRAVITY IS CALLED HYDROSTATIC EQUILIBRIUM