1. The Sun’s Structure & Features Chapter 26.1 Chapter 26.1 70% H 28% He The sun is made up of gas Temps: 15 million K at core / 5000 K at surface The sun gives off energy in all wavelengths of the ELECTROMAGNETIC SPECTRUM (Visible light, Infrared, X ray, gamma rays, etc)

2. Sun’s Energy: Nuclear Fusion When the star’s core gets hot enough (millions of degrees) Nuclear Fusion starts. Hydrogen + Hydrogen  Helium + ENERGY (+ neutron) Fusion continues to make heavier & heavier elements. Stops at Iron

4. Nuclear Fusion Nuclear Fusion is the process that releases energy on stars. It takes place in the core of the star. It starts when gravity pulls nebula together and temperatures increase to millions of degrees. In nuclear fusion, the nuclei (protons and neutrons) of atoms fuse together to make heavier elements and release energy. H + H  Helium + (neutron) + ENERGY

5. Fusion continues to produce heavier elements and release energy until IRON is made. Fusion stops with IRON. Elements heavier than Iron can only be made during the supernova explosion. The star will collapse or explode.

6. What keeps the sun stable? For a star to remain stable the force of GRAVITY must be balanced by the force of PRESSURE. Gravity – pulls sun inward (collapsing Thermal Pressure – pushes outward (keeping the sun from collapsing) –Cause of Pressure is heat from fusion When the sun runs out of “fuel”: When fusion stops  Heat decreases  Pressure decreases  GRAVITY WINS! (The star will collapse w/out Pressure pushing outward) Our sun will be stable for ~ 5 billion more years

7. The process that releases energy on stars is called __________________. This process takes place in the _________________ of stars. This process is initiated when ___________________ pulls most of the nebula’s mass into the center, and temperatures ___________________ ___________________________________________________________ Fusion starts by combining ________________ atoms (atomic # ____) together to make _________________, (atomic # _____). This process releases enormous amounts of ________________________. Fusion continues until heavy elements like _______________ are made. At this point, fusion __________ _______________ and the star will ____________________ or ___________________. Fusion does not take place on Earth because…

8. Interior Layers Core Fusion takes place ~ 15 million K Radiation Zone -Highly compressed gas -Energy travels by being emitted & absorbed as Electromag. waves -1 – 15 mill K -Takes 100,000 yrs for energy to travel through (dense) Convection Zone -Hot plasma closer to interior (1 million K) rises, cools (6000 K), and sinks in circular currents

9. Convection Currents

10. Surface Layers Photosphere - Lower atmosphere - Visible wavelengths - Temps. 6000 K Chromosphere - Middle atmosphere - Reddish – H atoms emit energy in red spectrum -Seen at Eclipses - Temps. 6000 – 10 000 K Corona - Upper atmosphere - Extends mill. Kms out - Millions of degrees (heated up by solar flares) - Becomes the source of solar wind

11. Ch. 26.1 Surface Features of the Sun A. Sun spots Cooler, darker regions on sun’s surface Associated w/Magnetic field Travel in groups – Move faster @ equator Last weeks / months B.Solar Prominences Loops of hot gas, associated w/sunspots C.Solar Flares Bursts of X-ray energy & particles Heat up corona to millions of K Particles form Solar Wind A C B

12. http://umbra.nascom.nasa.gov/eit/images/ Sun_and_earth.jpg

13. http://www.windows.ucar.edu/tour/link=/sun/images/sunspotnumbers_jpg_image.html http://www.windows.ucar.edu/tour/link=/sun/images/su nspots_max_min_big_jpg_image.html Solar Cycle: Pattern of sunspot activity ~ 11 year cycle Solar Max  Solar Max Solar Maximum: Peak # sunspots Solar Minimum: No or few sunspots

14. Particles from solar wind collide w/ Earth’s magnetic field at poles and create N. Lights (Aurora)

15. Links Sunspot activity & solar flare reports: www.spaceweather.com SOHO’s solar images: http://sohowww.nascom.n asa.gov/ What is a solar flare? http://hesperia.gsfc.nasa.g ov/sftheory/flare.htm Why study solar flares? http://hesperia.gsfc.nasa.g ov/sftheory/studyflare.htm Calculating the speed of CMEs: http://sohowww.nascom.n asa.gov/classroom/cme_a ctivity.html http://sohowww.nascom.n asa.gov/classroom/cme_a ctivity.html SDAC: http://umbra.nascom.nasa.govhttp://umbra.nascom.nasa.gov

16. Label the layers of the sun. B (Gives off visible light) C Normally not visible. Gives of red light A D E F 1.Label the Atmospheric Layers. 2. Give description of each layer. 3.Label the interior layers. 4. Give description of each layer.

17. Video Birth of the Solar System (National Geographic) http://www.youtube.com/watch?v=B1AXbpYndGchttp://www.youtube.com/watch?v=B1AXbpYndGc Massive Solar Storms (National Geographic) http://www.youtube.com/watch?v=DU4hpsistDk&feature=relmfuhttp://www.youtube.com/watch?v=DU4hpsistDk&feature=relmfu Massive Solar Storms http://www.youtube.com/watch?v=DU4hpsistDk&feature=list_related&playnext=1&list=SLhttp://www.youtube.com/watch?v=DU4hpsistDk&feature=list_related&playnext=1&list=SL