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Charles Hakes
Fort Lewis College
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Charles Hakes
Fort Lewis College
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Large Scale Structure
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Fort Lewis College
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Outline
• Homework (don’t forget them)
• Final Monday, 9:45.
• bring a scantron; good eraser, or extra
scantron; sharp pencils
• calculator
• Review Hubble’s Law
• Large Scale Structure
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Fort Lewis College
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Probable Job Opportunity
• The Academic Success Program
regularly funds Astronomy Tutors/
Study Group leaders. If you might be
interested in this for next fall, please
let me know via email.
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Fort Lewis College
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The Tully-Fisher Relation exists between
the galaxy's luminosity and its:
A) color.
B) size.
C) age.
D) rotation.
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Fort Lewis College
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The Tully-Fisher Relation exists between
the galaxy's luminosity and its:
A) color.
B) size.
C) age.
D) rotation.
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Fort Lewis College
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What method would be most appropriate to
determine the distance to a nearby galaxy?
A) Spectroscopic parallax
B) Cepheid variables
C) Hubble’s law
D) Radar ranging
Charles Hakes
Fort Lewis College
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What method would be most appropriate to
determine the distance to a nearby galaxy?
A) Spectroscopic parallax
B) Cepheid variables
C) Hubble’s law
D) Radar ranging
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Fort Lewis College
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Large-Scale Structure
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Fort Lewis College
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Figure 16.3
Cosmic Distance Ladder
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Fort Lewis College
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Large-Scale Structure
• Use the scale of 1m = 1 A.U.
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Fort Lewis College
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Large-Scale Structure
• Use the scale of 1m = 1 A.U.
• The Earth is 1 m from the Sun
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Fort Lewis College
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Large-Scale Structure
• Use the scale of 1m = 1 A.U.
• The Earth is 1 m from the Sun
• The Nearest star is near Albuquerque
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Fort Lewis College
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Large-Scale Structure
•
•
•
•
Use the scale of 1m = 1 A.U.
The Earth is 1 m from the Sun
The Nearest star is near Albuquerque
The center of the Milky Way galaxy
would be 4 times as far as the moon.
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Fort Lewis College
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Large-Scale Structure
•
•
•
•
Use the scale of 1m = 1 A.U.
The Earth is 1 m from the Sun
The Nearest star is near Albuquerque
The center of the Milky Way galaxy
would be 4 times as far as the moon.
• The Andromeda galaxy would be near
Mars
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Fort Lewis College
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Figure 16.3
Cosmic Distance Ladder
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Fort Lewis College
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Large-Scale Structure
• Redshift surveys of galaxies are used
to determine the large-scale structure
of the universe.
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Fort Lewis College
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Figure 16.9
First Galaxy Survey from the mid-1980’s
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Fort Lewis College
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Figure 16.10
The Local
Universe
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Fort Lewis College
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Large-Scale Structure
• Redshift surveys of galaxies are used to
determine the large-scale structure of the
universe.
• Observed structure includes:
• Strings
• Filaments
• Voids
• The most likely explanation is a slice
through “Bubbles.”
• Only a few of these “slices” have been
completed.
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Fort Lewis College
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Figure 17.1
Galaxy Survey
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Fort Lewis College
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Galaxy Survey
• The universe is homogeneous - it
looks the same everywhere
• The universe is isotropic - it looks
the same in all directions
• Cosmological principle - the
universe is isotropic and
homogeneous.
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Fort Lewis College
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Tools to study structure..
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Fort Lewis College
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Central Black Hole
• http://www.astro.ucla.edu/~ghezgroup
/gc/pictures/orbitsMovie.shtml
• ~4x106 Solar Masses
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Fort Lewis College
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Quasars
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Fort Lewis College
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Quasars
• Quasars are the active nuclei of very distant
galaxies. (Cannot observe the “rest” of the
quasar’s galaxy.)
• Energy output ~1000x Milky Way.
• Powered by material accreting onto a
supermassive black hole.
• Very large redshifts = Very distant.
• Can use spectra to study closer material.
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Fort Lewis College
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Figure 16.12
Twin Quasar
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Fort Lewis College
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Figure 16.13
Gravitational Lens
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Fort Lewis College
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Figure 16.14
Einstein Cross
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Fort Lewis College
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Figure 16.15
Galaxy Cluster Lensing
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Fort Lewis College
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Figure 16.16
Dark Matter Map
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Fort Lewis College
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Figure 16.11
Absorption Line “Forest”
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Fort Lewis College
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Review Questions
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Fort Lewis College
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RR Lyrae stars helped astronomers to:
A) Find the distance to nearby galaxies
B) Determine the center of the Milky Way
C) Verify spectroscopic parallax
D) Complete the H-R diagram
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Fort Lewis College
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RR Lyrae stars helped astronomers to:
A) Find the distance to nearby galaxies
B) Determine the center of the Milky Way
C) Verify spectroscopic parallax
D) Complete the H-R diagram
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Fort Lewis College
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What does the Hubble constant measure?
A) The density of galaxies in the universe
B) The luminosity of distant galaxies
C) The rate of expansion of the universe
D) the speed of a galaxy of known redshift
E) the reddening of light by intergalactic dust clouds
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Fort Lewis College
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What does the Hubble constant measure?
A) The density of galaxies in the universe
B) The luminosity of distant galaxies
C) The rate of expansion of the universe
D) the speed of a galaxy of known redshift
E) the reddening of light by intergalactic dust clouds
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Fort Lewis College
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What method would not be appropriate to
determine the distance to a nearby galaxy?
A) Tully-Fisher relationship
B) Cepheid variables
C) Hubble’s law
D) Type I Supernovae
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Fort Lewis College
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What method would not be appropriate to
determine the distance to a nearby galaxy?
A) Tully-Fisher relationship
B) Cepheid variables
C) Hubble’s law
D) Type I Supernovae
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Fort Lewis College
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Olber’s Paradox
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Fort Lewis College
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Olber’s Paradox
• Why isn’t the sky bright?
• If the universe is infinite, no matter which
way you look, you should see a star.
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Fort Lewis College
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Figure 17.2
Olbers’s Paradox
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Fort Lewis College
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Olber’s Paradox
• Why isn’t the sky bright?
• If the universe is infinite, no matter which
way you look, you should see a star.
• Since the sky is not bright, either…
• Universe is finite.
• Universe evolves with time.
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Fort Lewis College
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The Big Bang
• At some time in the past, everything
was at a single point.
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Fort Lewis College
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The Big Bang
• At some time in the past, everything was at
a single point.
1
Ho
time =
• When - Approximately 14 billion years ago.
• The Big Bang provides the resolution of Olber’s
Paradox
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Fort Lewis College
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Figure 17.3
Receding Galaxies - where was the Big Bang?
• The Big Bang happened everywhere
at once.
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Fort Lewis College
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Chapter 17
Ultra Deep Field - more than 1000 galaxies are in this
picture. Total estimate for the universe - ~40,000,000,000.
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Fort Lewis College
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Chapter 17
Cosmology
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Fort Lewis College
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Cosmology
•
•
•
•
How big is the universe?
How long has it been here?
How did it start?
How long will it last?
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Fort Lewis College
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The Fate of the Universe
• Will it keep expanding forever?
• Will gravity cause it to collapse?
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Fort Lewis College
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From closest to farthest, which methods are
used to find the distance to something?
A) radar, spectroscopic parallax, Cepheid variables
B) radar, RR Lyrae variables, spectroscopic parallax
C) parallax, Cepheid variables, RR Lyrae variables
D) Tully Fisher relation, Cepheid variables, parallax
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Fort Lewis College
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From closest to farthest, which methods are
used to find the distance to something?
A) radar, spectroscopic parallax, Cepheid variables
B) radar, RR Lyrae variables, spectroscopic parallax
C) parallax, Cepheid variables, RR Lyrae variables
D) Tully Fisher relation, Cepheid variables, parallax
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Fort Lewis College
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Interstellar gas is composed mainly of:
A) only hydrogen.
B) some hydrogen, but mainly carbon dioxide.
C) 10% hydrogen, 90% helium by numbers of atoms.
D) 75% hydrogen, 25% helium by weight.
E) ammonia, methane, and water vapor.
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Fort Lewis College
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Interstellar gas is composed mainly of:
A) only hydrogen.
B) some hydrogen, but mainly carbon dioxide.
C) 10% hydrogen, 90% helium by numbers of atoms.
D) 75% hydrogen, 25% helium by weight.
E) ammonia, methane, and water vapor.
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Fort Lewis College
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What is the single most important determinant
of the temperature, density, radius, luminosity,
and pace of evolution of a protostar?
A) its mass
B) its composition
C) its molecules
D) its magnetic field
E) its spin
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Fort Lewis College
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What is the single most important determinant
of the temperature, density, radius, luminosity,
and pace of evolution of a protostar?
A) its mass
B) its composition
C) its molecules
D) its magnetic field
E) its spin
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Fort Lewis College
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Which of these lies ahead for our Sun?
A) supernova of type II
B) brown dwarf
C) nova
D) planetary nebula
E) pulsar
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Fort Lewis College
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Which of these lies ahead for our Sun?
A) supernova of type II
B) brown dwarf
C) nova
D) planetary nebula
E) pulsar
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Fort Lewis College
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A massive object, heavier than the Sun,
which could fit inside a city, is a:
A) asteroid
B) white dwarf
C) neutron star
D) brown dwarf
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Fort Lewis College
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A massive object, heavier than the Sun,
which could fit inside a city, is a:
A) asteroid
B) white dwarf
C) neutron star
D) brown dwarf
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Fort Lewis College
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It is easiest to spot a newly formed
protostar with which types of telescopes?
A) ultraviolet scopes at the South Pole, through the
ozone hole
B) radio telescopes with the VLA in New Mexico
C) x-ray telescopes like Chandra, up in orbit
D) visible light scopes on Mount Palomar
E) infrared scopes on Mauna Kea
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Fort Lewis College
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It is easiest to spot a newly formed
protostar with which types of telescopes?
A) ultraviolet scopes at the South Pole, through the
ozone hole
B) radio telescopes with the VLA in New Mexico
C) x-ray telescopes like Chandra, up in orbit
D) visible light scopes on Mount Palomar
E) infrared scopes on Mauna Kea
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Fort Lewis College
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Three Minute Paper
• Write 1-3 sentences.
• What was the most important thing
you learned today?
• What questions do you still have
about today’s topics?
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Fort Lewis College
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