1. OUR STAR SOL

2. GOALS You will have a basic understanding of how a star functions and how they convert matter into energy You will discuss and write down key vocabulary related to the structure and functions within stars

3. JUST TO RECAP THE STATS WE KNOW… Age: 4.6 Billion years Diameter: 1,391,000 km Mass: 1.989 x 10^30 kg It’s a star It’s not on fire!!!!!

4. HISTORY… OR SOMETHING LIKE IT The Sun was revered by many ancient peoples.

5. EGYPTIANS The sun was revered as Ra. Carried across the sky in a Barque (ship) Accompanied by lesser gods for the daily journey

6. ANCIENT GREEKS The sun was hailed as Helios. Carried across the sky in a chariot drawn by fiery horses.

7. ROMANS Celebrated the birthday of the Sun as a holiday called “Sol Invictus,” literally “Unconquered Sun.”

8. MORE RECENT GREEKS The location of where the sun rose in the sky gave rise to the Zodiac. It was considered a planet

9. WHAT WE KNOW ABOUT THE SUN It is divided into 4 distinct layers Core Radiative Zone Convective Zone Photosphere Above this is the Atmosphere of the Sun

11. THE CORE 20-25% of the radius of the Sun 150 x density of water 15.7 million K 99% of the energy in the Sun is produced here

12. DETAILS OF FUSION Proton-Proton fusion happens 9.7 x 10^37 times each second in the core 6.2 x 10^11 kg /s of Helium is produced each second in this reaction About 1 x10^-13 x the mass of the Earth each second or 3.1169 x10^-19 x the Sun’s mass (slow enough for billions of years worth of fuel)

13. DETAILS OF THE FUSION CONTINUED… 0.7% of the mass of Helium produced is released as energy This equates to 3.846 x 10^26 Watts of energy per second 4.875 x 10^24 80 Watt lightbulbs for 1 second or… One 80 Watt bulb for 1.524 x 10^17 years

15. THE RADIATIVE ZONE 25-70% the radius of the Sun Temperature drops to between 7 and 2 million K

16. DETAILS OF THE RADIATIVE ZONE Temperature gradients within the zone are to high for convection to happen Energy is transferred by photons being emitted and absorbed by atoms

18. THE CONVECTIVE ZONE From about 70% of the radius of the sun to 200,000 km below its surface Temperatures low enough that atoms are no longer ionized Densities low enough that convection can occur

19. CONTINUED… Material is heated at the surface of the radiative zone and rises up where its energy is transferred to the photosphere Its temperature drops to 5700 K and then sinks back to the radiative zone to be reheated

21. PHOTOSPHERE The visible surface of the Sun 10 to 100’s of kilometers thick Observations of this layer resulted in the discovery of Helium