Our Star

Our Star SUN

Why does the Sun shine?

Ancients thought the Sun was made of ____. Why does the Sun shine? Ancients thought the Sun was made of ____.

Ancients thought the Sun was made of wood. Why does the Sun shine? Ancients thought the Sun was made of wood.

Others thought the Sun was made of ____. Why does the Sun shine? Others thought the Sun was made of ____.

Others thought the Sun was made of coal. Why does the Sun shine? Others thought the Sun was made of coal.

Why does the Sun shine? Astronomers of the 1800’s realized that coal or wood couldn’t account for the enormous energy of the Sun.

Why does the Sun shine? Astronomers of the 1800’s realized that coal or wood couldn’t account for the enormous energy of the Sun. There had to be a different way.

Why does the Sun shine? Kelvin and Helmholtz proposed a process called gravitational contraction to explain the energy of the Sun.

Why does the Sun shine? Kelvin and Helmholtz proposed a process called gravitational contraction to explain the energy of the Sun. Gravitational contraction could theoretically power the Sun for 25 million years.

Why does the Sun shine? Geologists found the Earth to be older than 25 million years which discounted gravitational contraction.

Why does the Sun shine? Geologists found the Earth to be older than 25 million years which discounted gravitational contraction. There had to be a different way.

Why does the Sun shine? In 1905 Einstein presented his E=mc2 equation. Mass could be converted to energy.

Why does the Sun shine? In 1905 Einstein presented his E=mc2 equation. Mass could be converted to energy. In the 1930’s other scientists using Einstein’s idea proposed nuclear fusion as the Sun’s energy process.

Why does the Sun shine? Theoretically, the center of the Sun had enough pressure and was hot enough to fuse hydrogen into helium releasing energy.

Why does the Sun shine? Theoretically, the center of the Sun had enough pressure and was hot enough to fuse hydrogen into helium releasing energy. The theory agreed with observation and was accepted. Later tests, especially dealing with neutrinos, confirmed this theory.

Why does the Sun shine? TWrT

Why does the Sun shine? TWrT 1) Why does the Sun shine?

Why does the Sun shine? TWrT 1) Why does the Sun shine? 2) How recent is this theory?

Why does the Sun shine? TWrT 1) Why does the Sun shine? 2) How recent is this theory? 3) What was the drawback to gravitational contraction as a theory for the Sun’s energy?

How does fusion work? Gas cloud in space

How does fusion work? Gravity causes gas to get closer and closer together  contraction.

How does fusion work? As the gas contracts, it becomes hotter. This is gravitational contraction.

How does fusion work?

How does fusion work? As the gas continues to heat up, it becomes plasma. Plasma – a state of matter, much like a gas, consisting of ions and free electrons.

How does fusion work? Eventually the center of the star becomes hot enough and has enough pressure to begin nuclear fusion.

How does fusion work?

How does fusion work?

How does fusion work?

How does fusion work?

How does fusion work?

How does fusion work? Gravity pulls the plasma closer and closer to the center of the Sun.

How does fusion work? Pressure from the extreme temperature of nuclear fusion pushes the plasma away from the center of the Sun.

How does fusion work? The pressure and gravity will find an equilibrium and exactly counteract each other called gravitational equilibrium.

How does fusion work?

How does fusion work? The purple line represents a photon’s path from the center of the Sun as it slowly moves outward.

How does fusion work? It takes hundreds of thousands of years for a photon to move from the center to the surface of the Sun.

How does fusion work? TWrT

How does fusion work? TWrT 1) How does the gas that forms the Sun heat up enough to perform nuclear fusion?

How does fusion work? TWrT 1) How does the gas that forms the Sun heat up enough to perform nuclear fusion? 2) Describe the plasma state of matter?

How does fusion work? TWrT 1) How does the gas that forms the Sun heat up enough to perform nuclear fusion? 2) Describe the plasma state of matter? 3) How many steps are needed for hydrogen to form helium through nuclear fusion?

Structure of the Sun

Structure of the Sun Core – where nuclear fusion occurs. (temperature > 15 million K)

Structure of the Sun Radiation Zone – where energy moves outward primarily in the form of photons (light). (temperature – 10 million K)

Structure of the Sun Convection Zone – where energy from the core moves outward transported by the rising of hot gas and falling of cool gas called convection. (temperature – 10 million K to 6,000 K)

Structure of the Sun Photosphere – top layer of the convection zone that is the visible surface of the Sun. (temperature – 6,000 K)

Structure of the Sun Chromosphere – layer just above the surface (atmosphere) of the Sun that radiates most of the Sun’s UV light. (temperature – 10,000 K)

Structure of the Sun Corona – outermost layer of the Sun’s atmosphere that emits most of the Sun’s x-ray light. (temperature – 1 million K)

Structure of the Sun Solar Wind – stream of charged particles blown outwards from the Sun. The solar wind extends well past the solar system.

Structure of the Sun TWrT

Structure of the Sun TWrT 1) Which section of the Sun is the hottest?

Structure of the Sun TWrT 1) Which section of the Sun is the hottest? 2) Which section of the Sun extends the furthest.

How do we know?

How do we know? Mathematical prediction and verification through experimentation.

How do we know? Photograph of Sun’s Photosphere

How do we know? Experiment showing Benard Cells which resembles Sun’s photosphere.

How do we know? Giant neutrino detectors which verify the predicted number of neutrinos from nuclear fusion in the Sun’s core.

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