Lecture 10: Cosmology and the Future of Astronomical...

Lecture 10: Cosmology and the

Future of Astronomical Research

1 Elizabeth Charlton, 2015

!  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

Elizabeth Charlton, 2015 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


!  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



"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

!  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 vr=Ho*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

!  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



"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


"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

(You are here)

!  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


!  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


!  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



"080998 Universe Content 240 after Planck" by NASA, Modified by User:⽼陳 - 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#mediaviewer/File:080998_Universe_Content_240_after_Planck.jpg

!  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

!  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


!  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



"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

"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


"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

!  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


!  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



"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

!  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


"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

!  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


!  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



"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

!  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


!  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


!  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


!  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



Copyright: ESA, Planck Collaboration


Copyright: ESA and the Planck Collaboration; NASA / WMAP Science Team

!  Age: 13.799 ± 0.021 billion years

!  Diameter: 92 Billion Light Years (Observable Universe)

!  Average Temperature: 2.72548K

!  Mass: at least 1053kg


!  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 Elizabeth Charlton, 2015

!  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


!  1 quadrillion (1015) 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


!  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

Lecture 10: Cosmology and the Future of Astronomical...

Documents

Transcript of Lecture 10: Cosmology and the Future of Astronomical...