Lecture 10: Cosmology and the Future of Astronomical Research 1
! The study of the Universe " Origin " Evolution " Eventual Fate! Physical Cosmology " Includes studies of large-scale structure and dynamics " Beginnings in Einstein s General Theory of Relativity! Recession of the Galaxies (Hubble s Law)! Expansion of the Universe 2
! Homogeneity " matter is uniformly spread through space " largest scales (>100 Mpc)! Isotropy " the universe looks the same in every direction " largest scales! Universality " the physical laws apply everywhere in the universe 3
! Electromagnetic radiation from an object is shifted to the red end of the spectrum! Mechanisms: " Doppler Effect change in frequency (wavelength) of an EM wave due to the motion of the source relative to the observer " Gravitational A shift in the wavelength of emitted EM radiation due to it moving out of a gravitational field " Cosmological an increase in wavelength of emitted EM radiation due to the expansion of the Universe 4
"Redshift blueshift" by Aleš Tošovský - Own work. Licensed under CC BY-SA 3.0 via Commons - https:// commons.wikimedia.org/wiki/file:redshift_blueshift.svg#/media/file:redshift_blueshift.svg 5
! Spectra of Galaxies had spectral lines shifted to longer wavelengths. " Red Shift " Analogous to Doppler Effect but not the same " Implied galaxies were receding! Hubble s Law General Law of Redshifts " Galaxy s velocity of recession is equal to a constant (H) times its distance v r =H o *d " Shows expanding universe "Redshift" by Georg Wiora (Dr. Schorsch) created this image from the original JPG.Derivative work:kes47 (talk) - File:Redshift.png. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/file:redshift.svg#mediaviewer/file:redshift.svg 6
! Cluster of Galaxies " 100s -1000s of gravitationally bound galaxies " examples: Local Group, Virgo Cluster! Superclusters of Galaxies " Larger group of galaxy clusters and galaxy groups " example: Local or Laniakea Supercluster! Filaments " Supercluster complexes " Largest structure in the Universe! hundreds of million to billions of light years 7
"Earth's Location in the Universe SMALLER (JPEG)" by Andrew Z. Colvin - Own work. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/file:earth %27s_Location_in_the_Universe_SMALLER_(JPEG).jpg#/media/File:Earth %27s_Location_in_the_Universe_SMALLER_(JPEG).jpg 8
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(You are here) "Local galaxy filaments RUS" by Klaus Dolag - http://www.mpa-garching.mpg.de/highlight/2002/ cr.gif. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/ File:Local_galaxy_filaments_RUS.gif#/media/File:Local_galaxy_filaments_RUS.gif 10
! A measure of the distance from which there is the possibility of retrieving information! Set the size and scale of the observable universe! Limitations: " Universal Expansion " General Relativity " Big Bang Cosmology 11
! Proper Distance " where a distant object would be at a specific point in cosmological time " can change over time due to universal expansion! Comoving Distance " factors out universal expansion " distance does not change with time due to the expansion of the universe At the present time proper distance and comoving distance are defined as equal 12
! Particle Horizon " represents the boundary between the observable and unobservable universe " largest comoving distance from which light emitted in the past could have reached an observer in a given time " distance defines the size of the present observable universe! Hubble Horizon " spherical region surrounding an observer beyond which objects recede from the observer faster than the speed of light " due to the expansion of the universe! Event Horizon " boundary where events cannot affect an outside observer " largest comoving distance from which light that is emitted now can reach an observer in the future " represents the maximum extent of the particle horizon " ~5Gpc! Future Horizon " events will be unobservable in the future as time goes to infinity " due to accelerating universe 13
"080998 Universe Content 240 after Planck" by NASA, Modified by User: 陳 - http://map.gsfc.nasa.gov/ media/080998/index.html updated data from http:// www.nasa.gov/mission_pages/planck/news/ planck20130321.html. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/ wiki/file: 080998_Universe_Content_240_after_Planck.jpg#media viewer/file: 080998_Universe_Content_240_after_Planck.jpg 14
! Recall: " The mass of the Milky Way was underestimated by the mass of its luminous matter alone. " Rotation Curve! graph of orbital rotation speed of stars or gas in the galaxy vs. its radial distance from the center of the galaxy "Rotation curve (Milky Way)" by Brews ohare - Own work. Licensed under Creative Commons Attribution- Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/ File:Rotation_curve_(Milky_Way).JPG#mediaviewer/File:Rotation_curve_(Milky_Way).JPG 15
! Type of matter that accounts for the gravitational effects of invisible mass " is not reactant to electromagnetic radiation! cannot be observed directly " Evidence! gravitational lensing! gravitational effects on visible matter 16
! Gravitational Lens " A distribution of matter capable of bending the light from a source as it travels to an observer " predicted by Einstein s theory of General Relativity 17
"A Horseshoe Einstein Ring from Hubble" by Lensshoe_hubble.jpg: ESA/Hubble & NASAderivative work: Bulwersator (talk) - Lensshoe_hubble.jpg. Licensed under Public domain via Wikimedia Commons - http:// commons.wikimedia.org/wiki/file:a_horseshoe_einstein_ring_from_hubble.jpg#mediaviewer/ File:A_Horseshoe_Einstein_Ring_from_Hubble.JPG "Einstein cross" by NASA, ESA, and STScI - http://hubblesite.org/newscenter/archive/releases/ 1990/20/image/a/. Licensed under Public domain via Wikimedia Commons - http:// commons.wikimedia.org/wiki/file:einstein_cross.jpg#mediaviewer/file:einstein_cross.jpg 18
"CL0024+17" by NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University) - http://hubblesite.org/ newscenter/archive/releases/2007/17/image/a/ (direct link). Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/file:cl0024%2b17.jpg#/media/ File:CL0024%2B17.jpg 19
! Hypothetical form of energy! Explains the acceleration of the expansion of the Universe " observed in the light from distant galaxies and supernova! Permeates all of Space 20
! Lamda-Cold Dark Matter Model of the Universe " Standard Model of Big-Bang Cosmology! includes the cosmological constant associated with dark energy and cold dark matter " Explains the following properties of the Universe:! the existence and structure of the Cosmic Microwave Background! the large-scale structure in the distribution of galaxies in the universe! the abundances of hydrogen, helium, and lithium! the accelerating expansion of the universe 21
"Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation" by User:Coldcreation - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/file:lambda- Cold_Dark_Matter,_Accelerated_Expansion_of_the_Universe,_Big_Bang-Inflation.jpg#mediaviewer/ File:Lambda-Cold_Dark_Matter,_Accelerated_Expansion_of_the_Universe,_Big_Bang-Inflation.jpg 22
! The current cosmological model for the early universe " First proposed by Georges Lemaître in 1927 " Based on the idea that the universe is expanding! hotter and denser in the past "Universe expansion2" by Original uploader was Gnixon at en.wikipedialater version(s) were uploaded by Papa November at en.wikipedia.(original text : en:user:gnixon) - Transferred from en.wikipedia(original text : Created by uploader from public domain source). Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/file:universe_expansion2.png#mediaviewer/ File:Universe_expansion2.png 23
"History of the Universe" by Yinweichen - Own work. Licensed under Creative Commons Attribution- Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/ File:History_of_the_Universe.svg#mediaviewer/File:History_of_the_Universe.svg 24
! Inflation " the exponential expansion of space in the early universe " explains the homogeneity and small-scale anisotropies of the cosmic microwave background " explains the observations that the universe is:! isotropic (the same in all directions)! flat 25
! Thermal radiation left over from the Big Bang " dates to 380,000 after the Big Bang " period of photon decoupling " expansion of universe has caused the wavelength of photons to increase over time 26
"Ilc 9yr moll4096" by NASA / WMAP Science Team - http://map.gsfc.nasa.gov/media/121238/ ilc_9yr_moll4096.png. Licensed under Public domain via Wikimedia Commons - http:// commons.wikimedia.org/wiki/file:ilc_9yr_moll4096.png#mediaviewer/file:ilc_9yr_moll4096.png 27
! Properties: " Black body spectrum with T=2.72458K " Peaks in the microwave wavelength of frequencies " Statistically uniform in all directions! current studies look at the small-scale anisotropies in the data! anisotropies expected in Big Bang Model 28
! Static Infinite Model " Spatially infinite and temporally infinite " Space is neither expanding or contracting " Requirements! Must explain the Cosmic Microwave Background, Hubble s Law, and provide a mechanism for the re-creation of Hydrogen 29
! Steady State Theory " Expanding Universe Model " Perfect Cosmological Principle! The Universe is the same in any time and any place " Though the Universe is expanding it does not change its appearance over time! New matter is continuously created as the Universe expands! Failed the observational test # Bright radio sources only exist in distant galaxies (in the distant past) # Cosmic Microwave Background 30
! Universe must be non-static! Problems: " structures have been found which are larger than the consistent scale predicted by the cosmological principle " Great GRB Wall (Hercules Corona Borealis Great Wall)! Possible Massive Galactic Superstructure (6 10 billion ly)! Observed via Gamma Ray Burst Mapping " Large-Scale Anisotropies in the Cosmic Microwave Background (Planck Mission)! Hemispheric Bias! Density! Average Temperature 31
Copyright: ESA, Planck Collaboration 32
Copyright: ESA and the Planck Collaboration; NASA / WMAP Science Team 33
! Age: 13.799 ± 0.021 billion years! Diameter: 92 Billion Light Years (Observable Universe)! Average Temperature: 2.72548K! Mass: at least 10 53 kg 34
! the Sun as a red giant: " expansion engulfs the orbits of Mercury, Venus, and possibly Earth " mass loss shifts the planets orbits outwards " habitable zone shifts to Saturn s moon Titan 35
! White Dwarf Sun ejects its outer layers leaving core behind " final mass loss could cause chaos for remaining planets! shifting orbits! collisions! ejection from Solar System! Black Dwarf White Dwarf s heat dissipates and the solar remnant cools " Sun s gravitational pull weakens " remaining planets become dark, frigid, and devoid of any life " due to mass loss the remaining planets orbit at further distances and more slowly around the solar remnant 36
! 1 quadrillion (10 15 ) years from now: " interactions with passing stars will completely strip the Solar System of its remaining planets " increased probability of interaction over time " THE END 37
! Depends on overall shape! Density Parameter " parameterized by Ω " Ω>1 closed universe! elliptical! Big Crunch " Ω<1 open universe! saddle shaped! Big Rip or Big Freeze " Ω=1 flat universe! Big Rip or Big Freeze! Also depends on the amount of Dark Energy "End of universe". Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/ File:End_of_universe.jpg#/media/File:End_of_universe.jpg 38