ASTRON 89 1nd Edition Lecture 15Outline of Last Lecture I. Helium is made in the Core II. Three Modes of Energy Transport in the Sun III. The Sun is in Hydrostatic and Thermal EquilibriumIV. Probing the Sun’s Interior V. The Photosphere VI. Sunspots Outline of Current Lecture I. The Sun’s Chromosphere II. The Sun’s Corona III. Solar Wind IV. Introduction to Properties of Stars Current LectureI. The Sun’s Chromosphere a. Above the photosphere b. Chromo means color c. Spicules: the temperature increases the higher and higher you go in the chromosphereII. The Sun’s Corona a. You can only see it when there is an eclipse (halo around the Sun)b. Extends to several million km c. But it’s only about a millionth as bright i. The Sun itself is much brighter (so you have to cover up the Sun to see itii. Streamers change depending on what activity is going on at the time iii. Corona changes its shape along with the sun spot activity d. Temperature of the corona is extremely high i. Temperature changes across the solar atmosphere (you think it gradually reducesii. What really happens at the surface (the height above the photosphere):1. Temperature decreases, but then suddenly increases. a. This is caused by the fact that a lot more material is carrying that energy, so at the corona there are little particles. It is less dense than the air that we breathe!These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. But the atoms that are in the corona are moving really fast (the faster that something moves, the hotter it is)e. The magnetic field of the Sun acts like a pump that increases the speed of particles in the coronaIII. Solar Wind a. Escapes the Sun from coronal holesb. Can be seen via X ray images c. The Sun is evaporating!i. The Sun is losing material. The wind carries away about 2 million tons of solar matter every secondIV. Introduction to Properties of Stars a. Properties: Distance, brightness, temperature, size, mass, chemical composition, ageb. Distance: i. Closest star to us: Proxima centaur (Alpha Centauri)ii. If Sun is marble, Earth is grain is sand one meter away. iii. Nearest star is another marble about 279 km awayiv. Parallax: phenomenon applicable1. Put your thumb out and close one eye. Close the other; note the difference in the location of your thumb. This is parallax2. Perspective is due to the rotation of the Earth (you can use the Earth’s motion to figure out how far it is by the amount of shift in the sky – you can measure angles in the sky). The shift in position tells you how far away, the farther away the smaller the anglea. The closer it is the larger the movement of the star. 3. D (distance to a star in pc) = 1 / p (parallax angle of that star in arc secondsa. Parsec comes from parallax in arc second4. 1 pc = 206,265 AU = 3.26