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MIT AST 101 - Lecture Slides

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Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine [email protected] 3HWs #6, #7, #8, and #9Exam #2SunSun videoSolar ConstantSlide 9Slide 10Slide 11Energy Source for SunSlide 13Slide 14Slide 15How does Fusion Convert Mass to EnergyE = mc2LawSlide 19ReactionAntiparticlesFusion reactionSlide 23Slide 24Proton-Proton Chain ReactionNeutrinosHow was the Homestake Gold Mine used to detect neutrinos?What was the solar neutrino problem?Solution of ProblemFusionWhat is happening to the amount of Helium in the Sun?Slide 32So how does the Sun stay relatively constant in Luminosity (power output)Slide 34Slide 35Slide 36Slide 37Parts of Sun CoreSlide 39Radiation zoneSlide 41Photons emitted from Fusion reactionsSlide 43Convection ZoneSlide 45Slide 46Slide 47Slide 48Slide 49Classification of StarsStars have different colorsSlide 52Surface TemperatureSlide 54Slide 55Who were these people?Fleming’s classificationAnnie Jump Cannon (1863-1941)More informationOBAFGKMSlide 61Slide 62Slide 63Slide 64ButSlide 66Slide 67Cecilia Payne-Gaposchkin (1900-1979)Slide 69Slide 70Slide 71Slide 72Slide 73Slide 74Hertzsprung-Russell DiagramSlide 76RememberSlide 78Slide 79Slide 80ClassificationsSlide 82RadiusSlide 84Main Sequence StarsSlide 86What does this tell usSlide 88Main Sequence LifetimesSlide 90AgesSlide 92Things to rememberSlide 94You need to know stellar classificationsSlide 96Slide 97Any Questions?Astronomy 101The Solar SystemTuesday, ThursdayTom [email protected]•Course Website:–http://blogs.umass.edu/astron101-tburbine/•Textbook:–Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny.•You also will need a calculator.•There is an Astronomy Help Desk that is open Monday-Thursday evenings from 7-9 pm in Hasbrouck 205.•There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http://www.astro.umass.edu/~orchardhill/index.html.HWs #6, #7, #8, and #9•Due by Feb. 23rd at 1 pmExam #2•February 25th•Covers from last exam up to todaySun•Brightest star in the sky•Closest star to Earth•Next Closest is Alpha Centauri, which is 4.3 light years awaySun video•http://www.space.com/common/media/video/player.php?videoRef=sun_stormSolar Constant•Energy received at Earth’s distance from the Sun•~1400 W/m2•50-70 % reaches Earth’s surface•30% absorbed by atmosphere•0-20% reflected away by cloudshttp://en.wikipedia.org/wiki/File: Sun_Life.pngAbsorption linesEnergy Source for Sun•Fusing hydrogen into helium–Hydrogen nucleus – 1 proton–Helium nucleus – 2 protons, 2 neutrons•Need high temperatures for this to occur•~10 to 14 million degrees Kelvinhttp://www.astronomynotes.com/starsun/s3.htmhttp://www.astronomynotes.com/starsun/s3.htmHow does Fusion Convert Mass to Energy•What is the most famous formula in the world?E = mc2•m is mass in kilograms•c is speed of light in meters/s•E (energy) is in joules•very small amounts of mass may be converted into a very large amount of energyLaw•Law of Conservation of mass and energy–Sum of all mass and energy (converted into the same units) must always remain constant during any physical processhttp://observe.arc.nasa.gov/nasa/exhibits/stars/star_6.html1 kg0.993 kg1 kg0.993 kg0.007 kgReaction•4 protons → helium-4 + 2 neutrinos + energyNeutrino-virtually massless, chargeless particlesPositron-positively charged electron – annihilated immediately by colliding with an electron to produce energyAntiparticles•Antiparticle – particle with the same mass and opposite electric charge•Antiparticles make up antimatter•Annihilation – when a particle and an antiparticle collide•Antimatter is said to be the most costly substance in existence, with an estimated cost of $62.5 trillion per milligram.Fusion reaction•Much more complicated than 4 protons → helium-4 + 2 neutrinos + energyDeuteron – Deuterium (hydrogen with a neutron)nucleusProton-Proton Chain Reaction•This reaction occurs ~1038 times each second•It if occurred faster, Sun would run out of fuelNeutrinos•Neutrinos – almost massless particles•No charge•It takes a neutrino about 2 seconds to exit the Sun•The neutrino was first postulated in 1930 by Wolfgang Pauli to preserve conservation of energy, conservation of momentum, and conservation of angular momentum during the decay of a neutron into a proton where an electron is emitted (and an antineutrino).•Pauli theorized that an undetected particle was carrying away the observed difference between the energy, momentum, and angular momentum of the initial and final particles.How was the Homestake Gold Mine used to detect neutrinos?•A 400,000 liter vat of chlorine-containing cleaning fluid was placed in the Homestake gold mine•Every so often Chlorine would capture a neutrino and turn into radioactive argon•Modelers predict 1 reaction per day•Experiments found 1 reaction every 3 days•Newer detectors used water to look for reactionsWhat was the solar neutrino problem?•Less neutrinos appeared to have been produced from the Sun than expected from modelsSolution of Problem•Neutrinos come in three types (slightly different masses)–Electron neutrino–Muon neutrino–Tau Neutrino•Experiment could only detect electron neutrinos•Fusion reactions in Sun only produced electron neutrinos•Electron neutrinos could change into other types of neutrinos that could not be detected•Neutrino oscillations – one type of neutrino could change into another typeFusion•The rate of nuclear fusion is a function of temperature•Hotter temperature – higher fusion rate•Lower temperature – lower fusion rate•If the Sun gets hotter or colder, it may not be good for life on EarthWhat is happening to the amount of Helium in the Sun?•A) Its increasing•B) its decreasing•C) Its staying the sameWhat is happening to the amount of Helium in the Sun?•A) Its increasing•B) its decreasing•C) Its staying the sameSo how does the Sun stay relatively constant in Luminosity (power output)http://www-ssg.sr.unh.edu/406/Review/rev8.htmlFigure 15.8Figure 15.4Temperature DensityParts of SunCore•Core – 15 million Kelvin – where fusion occursFigure


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MIT AST 101 - Lecture Slides

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