ASTR 1020 1st EditionExam # 1 Study Guide Lectures: 1 - 12 Ratios and Scaling RelationsEliminate constants and units by comparing quantities as a ratio2 x l 4 x A 8 x VLuminosity ~ TemperatureWeight ~ VolumeL = R^2 x T^4Light EquationsSpeed of light c = 3 x 10^8 m/secLights is a wave and particleHigh frequency = high energy = low wavelengthEM Spectrum ReviewCold  hotRadio – microwave – infrared – visible –UV – X-ray –gamma raysLarge wavelength = low frequency/energy, REDSmall wavelength = high frequency/energy, BLUEElectronic TransitionsThese 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.Emission –electron moves to lower level, emits photonPhoton Energy –difference in electron levelsAbsorption –electron moves to higher level absorbing a photonIonization –electron gains enough energy to escape atomPLASMA –fully-ionized gasEmission Line SpectraThin, hot gasses emit emission lineonly certain wavelengthsThermal Emission (black body)Dense body, shape determined by temperatureWein’s Law – T ~ (1/change of wavelength)Hotter = bluerStefan-Boltzmann Law – F ~ T^4Hotter = brighterAbsorption Line SpectraThin gas in front of a continuum sourcePhoton is absorbed if energy is exactDoppler Shif –measures speed of bright objectsBlueshif: shorter wavelength, higher frequency (moving toward observer)Redshif: longer wavelength, lower frequency (moving away)(Change in Wavelength / Wavelength) = [(WL observed – WL expected) / WL expected]~red 0.05 = v/c speed of lightFundamental Particles –each particles has an anti-particleparticle + anti =annihilationUp quark – in protons and neutrons, always groups of 3, charge +2/3Down quark - charge -1/3Neutrino –tiny mass, no charge, barely interact (only with weak force)Electron –negative charge, small mass, orbit nucleus determines atoms sizeFundamental ForcesGravity –all mass is attracted to all other mass (infinite range), relative strength=1Electromagnetism –atomic and molecular interactions (charge/infinite range)Weak Nuclear –mediates some radioactivity, range = 10^-18mStrong Nuclear –holds nuclei together, range = 10^-15m (nucleus) Proton-Proton Chain Fusion 4 x H  4He + energyIN  4 x Hydrogen nucleusOUT  4Helium, 2x neutrinos escape, 2x gamma rays (heat), + 2x positrons: (annihilated with electrons, x-rays=heat)The Solar ThermostatNEGATIVE FEEDBACK-one process happens then a second process happens to reverse the effects of the first processtoo cold – less fusion – contracts –heats – more fusion – expandsVisible Layers of the SunPhotosphere –visible “surface”, thermal spectrum, granulation, sunspotsChromosphere –very diffuse gas, emission line spectrum, prominencesCorona –very diffuse, emits X-rays, only seen during eclipsesSolar Wind/Heliosphere –top of corona evaporates + blows particles through solar systemInterior Layers of the SunCore p-p chain fusion, inward gravity balanced by outward pressureRadiative Zone –energy to random walk outward, no energy generatedConvection zone –hot material rises to surface (photosphere), cooler material sinks, top of convective cells are visible as granulation of photosphere WHAT WE SEESunspots and the Solar Cycle- Magnetic field loops cause sunspots, prominences- Cooler spot on photosphere, much hotter gas trapped above- Solar magnetic field “winds up” due to sun’s differential rotation: equator rotates faster than poles 11 years cycle of min-max solar activity Sun-Earth ConnectionCharged particles are deflected away from earth by magnetosphere Highest energy ones penetrate magnetosphere, strike Earth near magneticpoles AURORAStrong solar storms (coronal mass ejections) may damage satellites, astronauts, radio, +induce electric currentsParallax Distance- Measure distance to nearest stars using small angular shif in apparent position over the course of a yearDistance (parsecs) = 1/parallax angle (arcsec)1 parsec = 3.26 ly*measurements possible to about 100pcApparent Brightness vs. Absolute Luminosity Luminosity / (4 pi distance^2)- How bright a star appears on Earth- Luminosity=power emitted (size and temp)- 2 objects can have: luminosities, but not apparent brightness (because of distance)Spectral (Temperature) Classification: OBAFGKMOh Be A Fine Gorilla, Kiss Me !O –hot, hydrogen is ionized, massive, luminous, very blue/rareB, A –strong hydrogen lines, too hot for anything else, blue-white, luminousF, G –middle type, yellow, sun-like stars, moderate hydrogen/ionized metals linesK, M –red dwarf stars, low mass, cool enough that neutral metals and somemolecules can existMain Sequence Lifetimes- Higher mass stars have more fuel available, but burn through it much faster because they are much more luminouso 100 Msun star is 10^6 times more luminous than the suno 100x more fuel, burned 10^6x faster = 10^-4 times the lifespan Red dwarfs live foreverSun lives 10 billion yearsHigh-mass stars last millions of years**Star cluster ages can be determined by finding what masses of star are no longer on the MainSequence**- the lower mass (the “turning point,”) the older the cluster Range of Stellar PropertiesMass –core must be hot enough to fuse, but not self-destructRadius –depends on massLuminosity –depends on temperature and radiusTemperature –depends on massLifetime –depends on massMolecular Cloud Collapse = Gravity vs PressureIdeal Gas Law: (thermal pressure) P = nkT- pressure depends on density and temperature - pressure tries to expand cloud, gravity tries to crush it - If cloud mass is greater than the Jeans Mass, Gravity overcomes pressure o Molecular cloud (T~30 K, n=300 atoms/cm^3) must have >171 Msun to collapse - Gas cools via radiation (IR, radio photons) and keeps temperature constant as density increases Star Formation Life Track1. Molecular Cloud becomes protostar when radiation can no longer escape from interior 2. Protostar shrinks and heats as grav. potential energy is converted into thermal energy3. Shrinking slows and surface temperature rises as nuclear burning begins4. Fusion rate increases until grav. equilibrium is reached / stable star on Main SequenceEvolution of high-mass starsSame run-up from Main Sequence to Red Giant, but much faster- When on fuel runs out, core collapses and heats until hot enough to burn the next element (burning hotter and less time)-