physnotes_week_9.pdf PHYS 104-01
Popular in Astronomy
Popular in Astronomy
This 2 page Class Notes was uploaded by Sophie Stella on Sunday April 17, 2016. The Class Notes belongs to PHYS 104-01 at University of St. Thomas taught by Dr. Ruch in Winter 2016. Since its upload, it has received 18 views. For similar materials see Astronomy in Astronomy at University of St. Thomas.
Reviews for physnotes_week_9.pdf
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/17/16
PHYS 104: Astronomy Week 9 Course Notes, 3/30 – 4/1 (Week 8 consisted mainly of review for the test we took on 3/28, and the material covered can be found on previous pages of notes.) Definitions Fusion: The process of changing an element into a heavier element to release energy. Fission: The process of changing an element into a lighter element to release energy. Nutrinos: Aneutrally charged subatomic particle, used in the process of fusion. Incandescent: Emits light as a result of being hot. Photosphere: Protons that escape from the visible surface of the sun. (Radius is 696,000 km, and Temperature is 5,800 K) Corona: The hot, thin atmosphere of the Sun. (It has a low density and is about 1,000,000 degrees Convection Granules: Convection cells appear on the surface of boiling substances. There are convection cells on the sun, about 600 miles across each, which we call granules. Luminosity: The total amount of light emitted by an object in space. Apparent Brightness: Ameasurement of the light that reaches Earth from objects in space. Do not get Luminosity and Apparent Brightness confused. Absolute Magnitude: The intrinsic brightness of a star based on the magnitude system. Apparent Magnitude: The magnitude of a star as viewed from Earth on the magnitude scale. I. The Sun A. Amass of incandescent gas. B. Primarily made of hydrogen (which we know because of its emission lines). 1. 98% hydrogen and helium and around 1% of all of the other stuff on the periodic table. C. Evidence from pictures show convection cells on the sun's surface (which means the sun is boiling). D. The sun shines because it's hot. 1. 5800ºF 2. Everything with a temperature emits light. E. Pressure from the internal temperature is what keeps the sun inflated, while internal gravity keeps it contained. This is called Hydrostatic Equilibrium. 1. Without an internal energy source maintaining the temperature, the Sun would shrink. 2. The Sun is always losing radiation into space, which means it must have an internal energy source maintaining it. F. Structure (from inside to outside) 1. Hot, dense core a. This is where fusion reactions happen b. Only about 10 percent of the Sun’s mass will be converted to Helium. 2. Radiative Zone a. Energy carried by photons b. Does not absorb photons, but contains most of them within the sun. 3. Convective Zone a. Energy carried by convection b. Very good at absorbing light photons II. The Sun's Energy Source A. Nuclear Fusion 1. If the sun were burning energy, it would only last a few thousand years before it burnt up its entire mass. 2. If it were using gravitational energy, it would burn a few million years, but this still isn't long enough. 3. the Sun actually fuses hydrogen into helium, releasing energy. a. Fusion reactions are temperature-sensitive, which regulates the internal temperature of the Sun. (If the core cools down, the Sun contracts and increases its density, causing the reaction rate to speed up. If the core gets too hot, the sun expands, decreasing its reaction rate. Thus the sun stays at equilibrium.) 4. The Sun continues to use up hydrogen for energy, which means it has less hydrogen than when it started. B. The reaction rate 1. Depends on the composition a. Less hydrogen = lower reaction rate 2. Depends on the temperature a. Hotter = higher reaction rate b. As temperature decreases, pressure decreases (and the Sun shrinks). 3. As the core gains more and more helium, the reaction rate drops and the Sun shrinks. This, however, causes the core temperature to increase, causing the reaction rate to increase again and the Sun to grow.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'