Copyright © 2009 Pearson Education, Inc.Chapter 14Our GalaxyCopyright © 2009 Pearson Education, Inc.The math seminar you missedyesterdayThere will be a special seminar on Friday, November 13,1:50 p.m., Blocker 627:SPEAKER: Andrew Comech, TAMUTITLE:Operator version of the van der Corput lemma Cotlar-Stein almost orthogonality lemmaABSTRACT:Operator version of the van der Corput lemma and Cotlar-Stein almost orthogonality lemmaare two techniques often used in research on oscillatory integral operators.We will discuss how these results apply for the estimates on singular oscillatory integral operatorsin 1D and on nonsingular oscillatory integral operators in higher dimensions.No new results will be presented.Copyright © 2009 Pearson Education, Inc.We see our galaxy edge-on.Primary features: disk, bulge, halo, globular clustersCopyright © 2009 Pearson Education, Inc.Much of starformation in diskhappens in spiralarms.Whirlpool GalaxyIonization nebulaeBlue starsGas cloudsSpiral ArmsCopyright © 2009 Pearson Education, Inc.Spiral arms arewaves of starformation.Copyright © 2009 Pearson Education, Inc.Spiral arms are wavesof star formation:1. Gas clouds getsqueezed as theymove into spiralarms.2. The squeezing ofclouds triggers starformation.3. Young stars flowout of spiral arms.Copyright © 2009 Pearson Education, Inc.What have we learned?• How is gas recycled in our galaxy?— Gas from dying stars mixes new elements into the interstellarmedium, which slowly cools, making the molecular cloudswhere stars form.— Those stars will eventually return much of their matter tointerstellar space.• Where do stars tend to form in our galaxy?— Active star-forming regions contain molecular clouds, hotstars, and ionization nebulae.— Much of the star formation in our galaxy happens in the spiralarms.Copyright © 2009 Pearson Education, Inc.Since dust scatters blue light more thanred, stars seen through a lot ofinterstellar dust would lookA. Bluer than expected for their spectral typeB. Redder than expected for their spectral typeC. Fuzzy and unclear, just like this stupid lectureD. I don’t know, I am reading my emailE. Huh?Copyright © 2009 Pearson Education, Inc.About how long does light take to reachus from the nearest star besides the Sun?(The Sun takes 8 minutes.)A. About an hourB. About a weekC. About a monthD. About four yearsE. I don’t care, I’m majoring in marketingCopyright © 2009 Pearson Education, Inc.Which of the following is a viable way toestimate themass of our galaxy?A. Count all the stars and multiply by the average mass ofa starB. Make an estimate of the number of stars and multiply bythe average mass of a starC. Observe the speed of rotation using the Doppler shift.Knowing the orbital size and speed calculate the masswith Kepler’s lawD. A and CE. B and CCopyright © 2009 Pearson Education, Inc.When you calculate the Milky Way’smass usingthe two methods of the previous slide,what do you find?A. They agree pretty well.B. The mass you estimate for all the visible stars isonly about 1/10 the mass you get from observingmotions.C. The mass you estimate for all the visible stars isabout 10 times the mass you get from observingmotions.Copyright © 2009 Pearson Education, Inc.How do astronomers interpret theresults of the previous slide?A. They can’t because they are as stupid as a turnip.B. They know the answer, but aren’t gonna tell.C. 90% of the galaxy is unseen.D. There seems to be a new kind of matter–darkmatter.E. C and DCopyright © 2009 Pearson Education, Inc.About how long does light take to crossthe Milky Way Galaxy?A. About a monthB. About four yearsC. About 1,000 yearsD. About 100,000 yearsE. Millions of yearsF. There is no F on this friging clickerG. And no G too.Copyright © 2009 Pearson Education, Inc.Gas is added to the interstellar mediumby supernovae and planetary nebulae.What kind of gas would you expect thatto be?A. Hydrogen gasB. Helium gasC. Gas that has a mix of heavier elements in it,such as carbon, oxygen, silicon, iron, etcD. I don’t know, but the person next to me sureseems to be producing it.Copyright © 2009 Pearson Education, Inc.Chapter 15Galaxies and the Foundationof Modern CosmologyCopyright © 2009 Pearson Education, Inc.15.1 Islands of StarsOur goals for learning:• What are the three major types of galaxies?• How are galaxies grouped together?Copyright © 2009 Pearson Education, Inc.Hubble Deep Field• Our deepest imagesof the universe showa great variety ofgalaxies, some ofthem billions oflight-years away.Copyright © 2009 Pearson Education, Inc.Galaxies and Cosmology• A galaxy’s age, itsdistance, and the ageof the universe are allclosely related.• The study of galaxiesis thus intimatelyconnected withcosmology—thestudy of the structureand evolution of theuniverse.Copyright © 2009 Pearson Education, Inc.What are the three major types ofgalaxies?Copyright © 2009 Pearson Education, Inc.HubbleUltraDeepFieldCopyright © 2009 Pearson Education, Inc.HubbleUltraDeepFieldCopyright © 2009 Pearson Education, Inc.Spiral GalaxyHubbleUltraDeepFieldCopyright © 2009 Pearson Education, Inc.HubbleUltraDeepFieldSpiral GalaxyCopyright © 2009 Pearson Education, Inc.Elliptical GalaxyHubbleUltraDeepFieldSpiral GalaxyCopyright © 2009 Pearson Education, Inc.Elliptical GalaxyHubbleUltraDeepFieldSpiral GalaxyCopyright © 2009 Pearson Education, Inc.Irregular GalaxiesHubbleUltraDeepFieldElliptical GalaxySpiral
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