Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine [email protected] www.xanga.com/astronomy100OWL assignment (Due Next Thursday)Homework Assignment (Due by May 3)Homework Assignment (Due by May 5)Slide 5Astronomy Help DeskDistancesSlide 8White Dwarf SupernovaSlide 10Slide 11BecauseYou canSlide 14Tully-Fisher RelationSoSlide 17Slide 18Importance of Hubble’s Constant1/Hubble’s ConstantCalculationSlide 22Distant galaxies appear redshiftedSlide 24Slide 25Galactic FormationSlide 27How did Galaxies formSlide 29NextSlide 31Slide 32Slide 33Slide 34Slide 35Slide 36Why do galaxies differ?Slide 38OrSlide 40Galaxies CollideCollisionsIt appearsShow MoviesSlide 45Starburst GalaxiesSlide 47High Rate of Star FormationProducesSlide 50Slide 51QuestionsAstronomy 100Tuesday, Thursday 2:30 - 3:45 pmTom [email protected]/astronomy100OWL assignment (Due Next Thursday)•There is be an OWL assignment due on Thursday April 28 at 11:59 pm.•There are 15 questions and a perfect score will give you 2 homework points.Homework Assignment(Due by May 3)•Make up a test question for next test•Multiple Choice•A-E possible answers•1 point for handing it in•1 point for me using it on test•The question needs to be on material that will be on the 4th examHomework Assignment(Due by May 5)•I have placed 40 terms on the website•You get 0.1 of a HW point for each of these you define and hand in to me•Definitions need to be hand-written or hand-typed•A lot of these definitions will be on next test•Drake Equation•Dark Energy•Tully-Fisher Relation•ALH84001•Cepheid Variable•White Dwarf•Jocelyn Bell•Viking Mission•Hubble’s Law•SETI•Big Bang•COBE•Standard Candle•Quasar•Planck Time•Inflation in the Early Universe•Olber’s Paradox•Cosmic Microwave Background•Isotope•Baryon•Percival Lowell•Redshift•Dark Matter•MACHO•Critical Density•Radio Galaxy•Main Sequence Fitting•Cosmological Horizon•White Dwarf Supernova•Interstellar Medium•Supercluster•WIMPS•Pulsar•Habitable Zone•Maunder Minimum•Convection Zone•Radiation Zone•Hubble’s Constant•Starburst Galaxy•EuropaAstronomy Help Desk•There is an Astronomy Help Desk in Hasbrouck 205. •It is open Monday through Thursday from 7-9 pm.Distances•Distances are hard to measure in space•Apparent brightness = Luminosity 4 x (distance)2White Dwarf Supernova•White Dwarf Supernova are believed to be due to a white dwarf star that gains enough mass from a binary companion that it goes over the 1.4 solar mass limitWhite Dwarf Supernova•This causes the interior temperature to increase due to the increased gravity•Carbon fusion ignites throughout the star•The White Dwarf explodesBecause•These white dwarf supernova are all formed from white dwarfs of similar masses•Have similar maximum luminosities and similar lightcurvesYou can•Use the white dwarf supernova as a standard candle since you can determine its luminosityTully-Fisher Relation•The luminosity and rotation speed of a spiral galaxy depend on its mass•Luminosity depends on the number of stars, which is function of mass of galaxySo•If we measure the rotation speed of a galaxy•We can determine the galaxy’s luminosity•Use to determine distance since we can measure apparent brightnessImportance of Hubble’s Constant•Remember: v = d/t•d= vt•d = v/Ho •so t = 1/Ho •so if you know Hubble’s constant, you can determine the age of the universe1/Hubble’s Constant•Will equal the age if•The expansion rate has not changedCalculation•Hubble’s Constant = 71 km/s Mpc1 Mpc = 1000000 parsecs = 3260000 lightyears1 Mpc = 3.08 x 1019 kmHubble’s Constant = 2.305 x 10-18 s-1 1/Hubble’s Constant = 4.34 x 1017 s1/Hubble’s Constant = ~14 billion yearsDistant galaxies appear redshifted•Since galaxies are moving away from us, they appear redshifted•Wavelengths of features move to longer wavelengthsGalactic FormationNGC 1232How did Galaxies form•Usually assume two things:•Hydrogen and Helium filled all of space pretty uniformly at the beginning of the Universe•The Uniformity was not perfect and certain regions were denser than othersNext•The denser regions slowed their expansion and caused the material to contract into protogalactic clouds•Thought that stars in the spheroidal part formed firstNext•Collisions among gas particles tends to average out their random motions•Acquire orbits in the same direction and same planeNext•Star formation occurs in the disk•But not in the halo due to lack of gasWhy do galaxies differ?•Maybe due to spin of the protogalactic cloud•It was spining fast to begin with, you get Spiral•It was spinning slow to begin with, you get EllipticalOr•Elliptical galaxies may arise from denser protogalactic clouds•These would cool fast •Gas would form stars before they could settle into diskGalaxies Collide•Collisions happen over hundreds of millions of years•Probably occurred more frequent when the universe was smaller and galaxies were closer togetherCollisions•If two spiral galaxies collide•They may form elliptical galaxies•Large fraction of gas sinks to the center of the collision•Disks are torn apart•Star orbits are randomizedIt appears•That the Milky Way Galaxy and the Andromeda Galaxy will collide in about 5 billion yearsShow MoviesCartwheel Galaxy150,000 light years acrossStarburst Galaxies•Producing stars at ~100 per year•Milky Way Galaxy produces ~1 new star per yearArp 220High Rate of Star Formation•They would consume all their interstellar gas in a few hundred million years•High rate of star formation means very high supernova rateProduces•Galactic Wind is hot gas that erupts into interstellar space•Gas has temperatures of 10-100 million