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Astronomy Final Exam Overview:Earth is in the Milk Way Galaxy- located in the Disk of our universe- 1 of the 2 largest galaxiesLocal Group- group of about 40 galaxiesSolar System, Milk Way Galaxy, Local Group, Clusters of Galaxies (50-1000 gals) Nearest Cluster- VirgoVoids of space between Super clustersStars form inside clouds of gas/dust by the collapsing of gravityNuclear Fusion: 4 H -> He _releasing a lot of energyAfter stars die, the blow out most of the material they are made of and it is recycled to form new starsSolar System is made of recycled materialEarly Universe contained only H, He, and Li (98% H & He and 2% other). _ all other elements got there because of supernova explosionsThe Universe- 14 billion years oldIf something is 12 bill ly away- we see it 12 bill years ago ** when it was only 2 bill years old ** THE FURTHER AWAY WE LOOK IN DISTANCE, THE FURTHER BACK WE LOOK IN TIME ****Milky way- 100 billion starsAll of the galaxies are moving away from each other- the universe is expanding because of Hubble’s Law. In the past- galaxies were closer together!**** Beginning of the expansion- Big Bang Theory**** THE DISTANCE OF STARS IN GALAXIES DOES NOT CHANGE BC BOUND BY GRAVAccelerating charges produce light- electromagnetic radiation because light has both electric and magnetic fields ****Photons- energy in light waves transported by particles ****Light has: wavelength (distance between two peaks), a frequency (number of waves passing each second), a speed (300,000 km/s, always the same), an energy (depends on wavelength of frequ).**** Speed of light is always constantc = wavelength x freq**** As wavelength ^, frequency v ****E = Hubble’s constant x frequency**** Light with a SHORTER wavelength carries MORE energy ****Electromagnetic spectrum- light colors distinguished by frequency and wavelengthThe Sun- energy from THERMONUCLEAR RxN in the core: energy slowly moves outward through processes- cool dwarf star: spherical ball of hot gas- sunspots- Photosphere- visible layer of the sun, the “surface”, cant see passed the photosphereLimb darkening- looks darker at the edge than in the middleCentral Layers- core, radiation zone, convection zoneOuter Layers- photosphere chromosphere and coronaCore- nuclear fusion occurs hereRadiation zone- energy is transported by radiation. Convection zone- energy transported by convectionPhotosphere- outer layer of the sun, we see this layerChromosphere- very little lightCoronoa0 very hot due to magnetic fieldsSolar Wind- 10,000 km above photosphere- can escape suns gravitySunspots- low temperature regions in the photosphere, appear dark because cooler than surroundings, come and go in a few days, linked and produced by pairs of magnetic field lines, rotation of the sun drags magnetic field lines around with it cause kinks- 11 year sunspot cycle BUT really 22 years because they switch from northern to southern hemisphere every 11 yearsMagnetic field- produces solar activityLuminosity- total energy per second emitted by an object= power Solar flare- large explosion on suns surface emitting energy but in seconds rather than days like sunspotsSolar corona- larger and irregular than sunspot peak, hotter than photosphereCoronal mass ejection- emits charged particles that can affect the earthSolar wind0 escapes sun through CORONAL HOLES seen in XRAY IMAGESHydrostatic equilibrium- when gas pressure = gravity, the star is stable, reason why the sun does not collapse or expandWhen gas pressure > gravity – expandsGas pressure < gravity – contractsGas Temp- measure of moving atoms in random directionsGas Pressure- force of the atoms in their surroundings via there collisionsTemp ^ - Pressure ^Tem v – Pressure v Gravitational Contraction- keeps the sun shining for 40,000,000 yearsLuminosity- energy radiated by the sunNuclear Fusion- light nuclei into heavier nuclei and energy is produced as well, **** NEED temp of at least 10 million KE = m c ^2 ( c = speed of light )Law of conservation of mass and energy-mass and energy converted must always remain constant- you cant loose mass/energy, it just converted into the otherParticles created in Fusion- Deuterium (P & N), Positron (antiparticle of E- (+)), and Neutrino (charge-less and massless).Proton-proton chain- 4 H -> He + 2 neutrinos + energyMissing mass turns into Energy because of law of conserve. Of mass and energy**Neutrinos are hard to detect Fundamental Properties of Stars- - Size- Luminosity- Temperature- Mass- Distance- VelocityStars can range from .01 R to 1000 R IN SIZE ****Magnitude Scale- system of ranking stars by brightnessLuminosity- energy emitted by an object each second (total power), in Watts or J/s**** BIG HOT objects have GREATER LUM than SMALL COOL OBJ ****Brightness- how bright a source appears** BRIGHTNESS depends on DISTANCE ****** TO MAKE A STAR HAVE A GREATER LUMINOSITY  1. Make the star BIGGER in size or 2. Make the star HOTTER. ****To measure Luminosity-> we measure brightness with a CCD camera, records how much energy strikes its surface each secondMeasuring Temperature- Look at its colorRed- coolBlue- HotReddening- scatter away blue light, appears red but is really blueBlackbody radiation- opaque object that has a temp of 0k that produces radiation in the form of a continuous spectrum** the shorter the object the higher the temperature **Temperature is related to its peak wavelength. The SHORTER the peak of light emitted by the object, the HIGHER the objects temperature Hot objects emit light that peaks at SHORT/BLUE wavelengths ****Cool objects emit light that peaks at LONG/RED wavelengths ****GOOD BLACKBLODIES are not transparentPeak of BLACKBODY- tells us temperatureThree types of spectrum- (Kirchhoff’s laws)1. Continuous spectrum- hot/dense energy source (full rainbow)2. Emission line spectrum- hot low density cloud of gas (Black background with colored lines)3. Absorption line spectrum- Hot/dance energy source (rainbow with black cutouts)Atoms- “P & N, E- surrounding the atom, atoms are mostly empty spaceIsotopes- same number of protons different number of neutronsElectron- distribution of probability around the nucleus that behaves like a point particle on a fixed circular pathIonization- when an electron absorbs enough energy to escape the atom. It jumps off Photons- absorbed by an atom when an electron moves from LOWER to HIGHER energy level…. EMITTED when electron moves from higher to lower energy level Neon- red/orangeSodium- yellow**


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PSU ASTRO 001 - Astronomy Final Exam

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