1. Wednesday September 26, 2012 (Stellar Modeling; Videos – HTUW: Alien Galaxy – Part 4)

2. The Launch Pad Wednesday, 9/26/12 Which of the following would probably be the farthest from Earth? A.the Moon B.the Sun C.the Andromeda galaxy D.a large galactic cluster

3. The Launch Pad Wednesday, 9/26/12 How do galaxies evolve, and what holds them together? Young galaxies are messy and random in shape. As they grow older, gravity forms them into more organized shapes, like spirals or perhaps ellipses. A strong gravity source at the core (perhaps a massive black hole) helps to hold them together. “Dark Matter “ generates the gravity to “glue” the galaxy together.

4. The Launch Pad Wednesday, 9/26/12 What is the main difference between a refractive telescope and a reflective telescope? A refractive telescope bends light rays through a tube using glass lenses. A reflective telescope bounces light through a tube using mainly polished mirrors.

5. Announcements Happy Weekend!

6. Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day Quiz 3S39/14 9/28 Lab – Distance and Spacing of the Planets F69/179/18 Lab – Comparing the Terrestrial and Jovian Planets F79/189/19 Quiz 4S49/21 10/5

7. ?? Recent Events in Science Curiosity Finishes Close Inspection of Rock Target NASA's rover Curiosity touched a Martian rock with its robotic arm for the first time on Sept. 22, assessing what chemical elements are in the rock called "Jake Matijevic." http://www.nasa.gov/mission_pages/msl/ne ws/msl20120924.html Watch the Video!

8. Video How the Universe Works: Alien Galaxy Part 4 - Dark Matter: Glue of the Universe (17:40 – 23:15)

9. Project – Stellar Modeling

10. Stellar Modeling The core of a star is a very hot, dense region where nuclear fusion releases gamma and x-ray radiation. The radiation zone is outside of the core where radiation diffuses outward over millions of years. The convection zone is structured by hot material rising from the interior, cooling, and sinking. The upper reaches are the visible “surface” of a star Our Sun’s surface temperature is about 5,800 K.

11. Stellar Modeling

12. Solar Structure

13. Our Star The Sun’s structure can be divided into four parts: the solar interior the photosphere the chromosphere the corona

14. Regions of the Sun

15. The Solar Interior The interior of the Sun cannot be observed directly. Thermonuclear fusion occurs here in the deep interior, and this fusion is the source of the Sun’s energy. The thermonuclear reaction that produces the Sun’s energy is called the proton– proton fusion reaction.

16. The Solar Interior Inside the Sun, matter is converted to energy (recall Einstein’s equation E = mc 2.) 600 million tons of hydrogen is consumed each second. The Sun has burned for about 4.5 billion year, yet has enough fuel to last another five billion years.

17. The Photosphere The term “photosphere” means “sphere of light.” This is the “surface” of the Sun – it’s actually a layer of incandescent gas less than 500 kilometers thick. The photosphere is about 90% hydrogen and 10% helium. It has a grainy texture made up of many small, bright markings, called granules (each perhaps the size of the Earth), which are produced by convection of the Sun’s hot gases. Most of the elements found on Earth also occur on the Sun in tiny quantities The surface temperature averages about 6,000 K (10,000°F.)

19. The Chromosphere The chromosphere lies just above the photosphere - it’s the Sun’s lowermost atmosphere. It’s a relatively thin, hot layer of incandescent gases a few thousand kilometers thick. The top layer of the chromosphere contains numerous spicules, which are narrow jets of rising material incandescent plasma.

21. Spicules of the Chromosphere Figure 23.24

22. The Corona The corona is the outermost portion of the solar atmosphere, and is very tenuous (meaning very thin.) Ionized gases escape from the outer fringe and produce the “solar wind.” The temperature at the outer edge of the corona exceeds 1 million K.

23. Figure 23.25 The solar corona is visible only during a solar eclipse.

24. Solar Features - Sunspots Sunspots exist on the solar surface, and follow an 11-year cycle. Sunspots have a dark center (the umbra) surrounded by a lighter region (the penumbra.) The dark color is due to a cooler temperature, 1,500 K less than the solar surface. Large sunspots are strongly magnetized, with pairs have opposite magnetic poles.

25. Plages are bright centers of solar activity that occur above sunspot clusters. Prominences are huge arching cloudlike structures that extend into the corona that are caused by condensations of material in the corona. Solar Features – Plages and Prominences

26. Solar flares are explosive events that normally last an hour or so. There is a sudden brightening above a sunspot cluster that releases enormous quantities of energy. Flares eject particles that reach Earth in about one day and interact with the atmosphere to cause the auroras (the Northern and Southern Lights.) Solar Features – Flares

27. A coronal mass ejection(CME) is a massive burst of solar wind and magnetic fields rising above the solar corona or being released into space. Solar Features – Coronal Mass Ejections