OUR STAR SOL

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

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!!!!!

HISTORY… OR SOMETHING LIKE IT

• The Sun was revered by many ancient peoples.

EGYPTIANS

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

journey

ANCIENT GREEKS

• The sun was hailed as Helios.• Carried across the sky in a chariot drawn by

fiery horses.

ROMANS

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

MORE RECENT GREEKS

• The location of where the sun rose in the sky gave rise to the Zodiac.• It was considered a planet

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

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

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)

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

THE RADIATIVE ZONE

• 25-70% the radius of the Sun• Temperature drops to between 7 and 2

million K

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

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

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

PHOTOSPHERE

• The visible surface of the Sun• 10 to 100’s of kilometers thick• Observations of this layer resulted in the

discovery of Helium