ASTR 1120General Astronomy:Stars & Galaxies• FINAL: Saturday, Dec 12th, 7:30pm, HERE• ALTERNATE FINAL: Monday, Dec 7th, 5:30pmin Muenzinger E131• Last OBSERVING session, Tue, Dec.8th, 7pm• Please check your grade on clickers, midterms,HWs on CU learn - e-mail Thomas if you seediscrepancies/missing grade.Review of the CourseFour general topics:1. Intro: Scales, matter, light, telescopes2. Stars3. Galaxies4. Cosmology/Dark Matter/UniverseTo develop a broad view ofwhat we know about theUniverseTo understand the forcesthat shape the Universeand its historyTo help you understandhow we figured all this outTo learn how science worksCourse Goals1. The Scale of the UniverseMatter: Atomnucleuselectrone-protonsneutronsp+nLight: our main source ofastronomical knowledgeThe Electromagnetic spectrumThermal (black body) Spectra• Emitted by allsolid/opaque objects,including stars,planets, humans• Smooth, broadspectrum rising to apeak at somewavelength, wheremost of the radiation isemitted– Wien’s Law– Stefan-Boltzmann LawSpectral lines: By atoms emittingor absorbing PHOTONS = light• The energychange betweenlevels is equal tothe energy of thephoton.• Remember-larger energyjumps will beSHORTERwavelengthphotons!Telescopes• Refracting vs Reflecting• Size matters:– Light gathering power– Angular resolution (diffraction limit)• Telescopes are built differently for differentwavelengths: ground-based, airborne and space1. What is the Sun made of?2. How does the Sun produce its energy?3. Which forces keep the Sun inequilibrium?4. What’s inside the Sun?5. What will be the end of the Sun?6. How massive is the Sun?Stars: Starting with our SunStars• Shine with energyreleased from fusion– hydrogen fusing intohelium• Overall fusion rate verystable– gravitational equilibrium• Violent activity on thesurfaceMeasuring the Stars• Estimating distances viaparallax• Inverse square law forbrightness– Apparent brightness anddistance ! luminosity• Measuring temperaturesvia color, spectral type– OBAFGKM• Measuring masses viabinary starsThe Hertzsprung-Russell DiagramThe Main Sequence• Stars spend most oftheir lives here• More massive stars are– Rarer– Hotter/Bluer– Brighter– Shorter lived• Can estimate ages ofstar systems from“main sequenceturnoff”Stellar Evolution1. Star Birth2. Main Sequence3. Series of expansionsand deflations inresponse to corenuclear burning• Low mass stars:– Red giant– Horizontal branch star– Planetary nebula– White dwarfStellar Evolution1. Star Birth2. Main Sequence3. Series of expansionsand deflations inresponse to corenuclear burning• Low mass stars:– Red giant– Horizontal branch star– Planetary nebula– White dwarfHigh Mass Stars• Very rapid sequencefusing heavier elementsup to iron– Core unsupported =collapse• Supernova explosion– Blasts heavy elementsback into space• Neutron star or blackhole remainsStellarGraveyard• White dwarfs– and the possibility ofwhite dwarf supernovae• Neutron stars– possible pulsars• Black Holes– Detected only by theirinteractionsStellarGraveyard• White dwarfs– and the possibility ofwhite dwarf supernovae• Neutron stars– possible pulsars• Black Holes– Detected only by theirinteractionsStellarGraveyard• White dwarfs– and the possibility ofwhite dwarf supernovae• Neutron stars– possible pulsars• Black Holes– Detected only by theirinteractions3. The Milky Way Galaxy• Our home spiral galaxy– Bulge– Halo– Disk• Star-Gas-Star Cycle– Gas– Dust– Stars• A supermassive blackhole in the GalacticCenter?!– Yes3. The Milky Way Galaxy• Our home spiral galaxy– Bulge– Halo– Disk• Star-Gas-Star Cycle– Gas– Dust– Stars• A supermassive blackhole in the GalacticCenter?!– Yes3. The Milky Way Galaxy• Our home spiral galaxy– Bulge– Halo– Disk• Star-Gas-Star Cycle– Gas– Dust– Stars• A supermassive blackhole in the GalacticCenter?!– YesSgr A*Other Galaxies• Main Galaxy types:– Spirals– Ellipticals– Irregulars• Bulges/spheroids– Older (Population II)• Disks– Forming stars today(Population I)AGNs Central EnginesHow do AGNs emit somuch light in so littlespace?• They are powered byaccretion disks aroundsupermassive blackholes• In some AGNs, hugejets of material are shotout at the poles. Thesejets are strong radiosources.JETDISK“Distance Ladder” to measure universeDifferent standard candles are usefulfor different distancesDiscovery of anExpanding Universe• Hubble’s Law• The distancesbetween galaxies aregetting bigger!• Running timebackwards ! age ofthe universeGalaxy Evolution• Galaxy formation– Observe galaxies atdifferent redshifts(lookback times)– Assemble sequence• Galaxy interactions– Spirals ! Ellipticals– Active and starburstgalaxies• Check via computermodels of gas, gravity,and star formation4. Cosmology/Dark Matter• Spiral galaxy rotation curves and galaxy clusters (3ways) suggest large amounts of DARK MATTER– 90% of the universe is a type of matter we can’t see!!• Most likely candidate:– WIMPs• Probably an unidentified subatomic particleThe Fate of the Universe• Hubble constant setsthe expansion rate forNOW• Dark matter pullsexpansion curvesdownwards• Upwards curvesuggests DARKENERGY pushingagainst gravity???!TheCreationof theUniverseEvidence for the Big Bang• Expanding universe• Cosmic microwavebackground• H/He content of theuniverse• InflationCarl Sagan: Author of “A Pale BlueDot” “The Demon-Haunted World”,“Contact”, “Cosmos”, …We succeeded in taking that picture [from deep space], and, if youlook at it, you see a dot. That's here. That's home. That's us. On it,everyone you ever heard of, every human being who ever lived, lived outtheir lives. The aggregate of all our joys and sufferings, thousands ofconfident religions, ideologies and economic doctrines, every hunter andforager, every hero and coward, every creator and destroyer ofcivilizations, every king and peasant, every young couple in love, everyhopeful child, every mother and father, every inventor and explorer,every teacher of morals, every corrupt politician, every superstar, everysupreme leader, every saint and sinner in the history of our species, livedthere on a mote of dust, suspended in a sunbeam. I wish you good luck with the Final Exam -- please bring a #2 pencil and ID… and I hope you’ve enjoyed thiscourse that has