The General Properties of the Sun

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1 Notes:

2 The General Properties of the Sun The sun is an average star with average brightness. It only looks bright because it s so close. It contains 99% of the mass of the solar system. It is made of entirely of gas Light from it takes 8.32 minutes to get to Earth.

3 The Solar Interior The sun s interior consists of 3 layers: Core: where fusion happens. This is where the sun gets its energy from. Radiative zone: where energy from the core is carried to toward the surface as light. Convective zone: where energy is carried further toward the surface as heat.

4 Energy Production in the Interior Energy in the sun (and all other stars) is created using nuclear fusion. Nuclear fusion: the combination of 2 or more lighter atomic nuclei to produce heavier ones.

5 Nuclear Fusion There are three steps in nuclear fusion: 1. Two H protons collide and fuse. One emits a positron and becomes a neutron.

6 Nuclear Fusion 2. Another H atom fuses to create a 2 proton, 1 neutron nucleus known as He-3

7 Nuclear Fusion 3. Two He-3 nuclei each containing 2 H protons and 1 neutron collide and fuse. This releases 2 protons of H. The remaining 2 protons and 2 neutrons fuse to form Helium-4 Energy released during fusion causes the sun to shine and gives the sun its high temperature

8 Nuclear Fusion Mass lost from fusion becomes energy Albert Einstein small amount of matter yields a large amount of energy E=MC2 E=energy M=mass C=speed of light Fusion takes advantage of E = mc 2. Matter (hydrogen) gets converted to helium and ENERGY. The sun needs to transform 5 million tons of mass into energy every second to counter its own gravity.

9 The Sun s interior is held stable by a balance between radiation pressure forces and gravity, in a condition called hydrostatic equilibrium. GRAVITY pulls in RADIATION PRESSURE FROM HYDROGEN FUSION pushes out

10 The Solar Atmosphere The atmosphere of the sun is only visible to us during solar eclipses. It is broken up into 3 layers: Photosphere: the apparent surface of the sun. This is where the light we see comes from. Chromosphere: the reddish layer just above the photosphere. Corona: the biggest and hottest layer. Visible Ultraviolet Corona Photosphere Chromosphere

11 The Photosphere The apparent surface of the sun. It absorbs radiation from the interior and re-emits it into space. Energy from the core must be transported outward. This is done through convection. Hot gas bubbles up from the interior, then they cool and sink back down. The bubbles last minutes. The visible result of convection is granulation. It creates a grainy-like appearance to the photosphere. Real picture of granules Cool gas sinking down Bubbles of hot gas rising up 1000 m

12 The Chromosphere Found just above the photosphere. Emits only certain wavelengths of visible light, resulting in a reddish appearance. Characterized by jets of gas rising from the photosphere called spicules. Spicules last about 5-15 minutes.

13 The Corona The outer atmosphere of the sun. It s the biggest and hottest layer of the solar atmosphere. The sun is constantly losing mass. The mass being lost is called the solar wind.

14 The Sun and Magnetism The sun rotates faster at its equator than its poles. The magnetic field creates different features: Sunspots, prominences, solar flares, and coronal mass ejections (CMEs)

15 Sunspots Cooler regions of the photosphere that appear dark. Sunspots are related to magnetic field activity in the photosphere. Magnetic field lines emerge from sun spots. The number of sunspots varies in a 11 year cycle.

16 The Solar Cycle After 11 years, the magnetic field pattern becomes so complex that it is re-arranged. The new magnetic field structure is similar to the original, just reversed. a new, 11-year cycle begins.

17 Prominences Phenomena in the corona in which gas appears to erupt from the corona and loop back into the sun.

18 Solar Flares Sometimes a prominence is ejected out into space, creating a solar flare. Solar Flare

19 Coronal Mass Ejections (CMEs) Occur when immense (2 trillion tons) quantities of solar material are ejected into space at immense (4 million mph) speeds. They are created when magnetic field lines, which normally snake around each other, connect, essentially short circuiting the system. An x-ray view of a coronal mass ejection It reaches Earth two to four days later, and is fortunately deflected by our magnetic field.

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