Our Sun & Nuclear Fusion (Power Point 13) Image Credit: NASA

Student Learning Objectives Construct a model of the solar system Describe the layers of the Sun and how energy is transported through each layer Explain sunspots and solar activity. Image Credit: APOD

https://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=188 Image Credit: NASA

What do we know about the Sun? 4 x 1026 Watts 100 times hotter than Earth’s hottest summer day 300,000 times more mass than Earth 109 Earth diameters 1,300,000 Earth volumes Sun Earth Surface Temperature 9,944 °F 57.2 °F Mass 1.988 x 1030 kg 5.976 x 1024 kg Diameter 1,392,000 km 12,756 km Density 1.5 g/cm3 5.5 g/cm3

Energy Transfer Energy is transported from hot to cold, through the layers of a star, by two methods. Radiation (light) Convection (boiling) Image Credit: Creative Commons

Practice Does the Earth emit electromagnetic radiation? Is the Sun a relatively hot or cool star? Can convection occur in air? Explain.

What are the layers of the Sun? Image Credit: NASA

The Layers Core: energy production Radiative Zone: photons travel from core through this layer Convective Zone: boiling fluid transfers energy Photosphere: photons leave star Surface of the Sun Limb Darkening Granulation bubbles size of Texas last 10-20 minutes

Recorded at Big Bear Solar Observatory https://www.youtube.com/watch?v=O-UjQwTfjGg Recorded at Big Bear Solar Observatory

Chromosphere: thin jets of gas called spicules Corona: solar wind Transition Zone Temperature spikes Corona: solar wind protons, electrons, and other small particles leave the Sun

Corona Image Credit: APOD http://apod.nasa.gov/apod/image/0907/corona_vangorp_big.jpg Corona Image Credit: APOD

Practice In which layer of the Sun is energy produced? Describe a spicule. List the layers of the Sun.

Density & Temperature (Core  Outward) Density decrease rapidly from core through corona. Temperature decreases rapidly from core through photosphere. Temperature spikes up in the chromosphere. Image Credit: University of Northern Iowa

Practice Why does the corona escape the Sun? How do astronomers know the layers of the Sun? Hint: How do we know about the interior of the Earth? Why is the photosphere called the surface? Which layer(s) is/are the atmosphere of the Sun?

What mechanism is responsible for sunspots? A sunspot is a relatively cooler area on the surface of the Sun. T = 4,240 Kelvin (8,155 ○F)   Change in size Last days or months Appear in pairs and groups Image Credit: NASA

http://apod.nasa.gov/apod/ap110928.html Image Credit: APOD

Sunspots form where energy is disrupted by kinks in the magnetic fields. Differential rotations cause the magnetic field to become “tangled” resulting in "kinks" in the magnetic field lines. Babcock Model

Differential Rotation & Sunspot Cycle Different layers in the Sun rotate with different speeds. Different latitudes on the surface rotate at different speeds. Equator = 25 days Poles = 27.8 days The sunspot cycle peaks every 11 years Full Cycle = 22 years N-S to S-N S-N back to N-S http://spaceweather.com/

Image Credit: NASA

Practice A 60 Watt light bulb is 250 ○F. Would an 8,155 ○F sunspot be bright if it was isolated from the surrounding photosphere? How would the energies compare for the 60 Watt Light Bulb and a sunspot? Hint: Energy depends on T4

The Zeeman Effect shows strength of magnetic field. Atomic energy levels are split into sublevels Degree of splitting  strength of field All activity observed on the surface of the Sun, and in the solar atmosphere, is caused by the Sun’s magnetic field. Image Credit: NASA

What are the features that indicate solar activity? Prominence Image Credit: APOD

Filament Flare Image & Video Credit: NASA & Spaceweather.com

Practice Differentiate between a solar prominence and a solar filament. How are prominences and filaments different from flares? Can solar activity affect us on Earth?

How do stars produce photons? The definition of a star is an object that has a core density great enough to sustain nuclear fusion. Proton–Proton Chain 4 H  He + energy

1 Second in Our Sun 1038 reactions 600 billion kg Hydrogen converted into Helium 4 billion kg of mass becomes energy https://www.nasa.gov/centers/goddard/news/topstory/2007/soho_heart_of_sun.html Image Credit: NASA

Practice Our star will last another 5-6 billion years. How is this possible with so much mass loss each second? What are the contributing factors for how long a star will live?