Our Sun & Nuclear Fusion (Power Point 11) 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 Video Credit: APOD

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

Bubbles the size of Texas The Layers Core: energy production takes place here Radiative Zone: photons leave the core and travel through this layer, transferring energy by radiation Convective Zone: boiling fluid transfers energy in this layer Photosphere: photons leave star Surface of the Sun Limb Darkening at edges Granulation on surface Bubbles the 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: this layer is comprised of thin gas jets called spicules Transition Zone Temperature spikes Corona: constantly changing solar wind Comprised of small particles (p, e−, etc.) Mass leaves 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, and state the type of energy transfer that occurs in that layer.

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 Explain why the corona is able to 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)   Spots change in size Sets of spots will last days or months Spots always appear in pairs Image Credit: NASA

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

Sunspots form where energy is disrupted by the magnetic field. 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 to N-S http://spaceweather.com/

Solar Cycles Image Credit: NASA

Practice A 60 Watt light bulb is 250 ○F. Explain why an 8,155 ○F sunspot appears to be dark. How would the energies compare for the 60 Watt Light Bulb and a sunspot? E = sT4

Solar Activity The Zeeman Effect shows is used to determine the strength of a magnetic field. Atomic energy levels are split into sublevels Degree of splitting indicates 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.

Zeeman Effect 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 Name the two ways our star, the Sun is losing mass. 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?