A100–Exploring the Universe: Discovering Galaxies
Martin D. Weinberg
UMass Astronomy
astron100-mdw@courses.umass.edu
November 13, 2014
Read: Chaps 19, 20
11/13/14 – slide 1
Announcements
⊲ Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Read: Chaps 19, 20
Exam #2 questions returned after class today
Solutions posted on the website in the “exams” tab. See
http://courses.umass.edu/astron100-mdw
11/13/14 – slide 2
Announcements
⊲ Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Read: Chaps 19, 20
Exam #2 questions returned after class today
Solutions posted on the website in the “exams” tab. See
http://courses.umass.edu/astron100-mdw
Begin by reviewing top 4 low-scoring exam questions
Today: Galaxies
⊲
⊲
⊲
What are the three major types of galaxies?
How are galaxies grouped together?
How do we determine distances to galaxies?
11/13/14 – slide 2
Announcements
⊲ Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Read: Chaps 19, 20
Exam #2 questions returned after class today
Solutions posted on the website in the “exams” tab. See
http://courses.umass.edu/astron100-mdw
Begin by reviewing top 4 low-scoring exam questions
Today: Galaxies
⊲
⊲
⊲
What are the three major types of galaxies?
How are galaxies grouped together?
How do we determine distances to galaxies?
Your questions?
11/13/14 – slide 2
Discussion of exam questions: #39
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Degeneracy pressure is the source of the pressure that stops
the crush of gravity in all of the following except
Read: Chaps 19, 20
(A) a brown dwarf.
(B) a neutron star.
(C) the central core of the Sun after hydrogen fusion ceases
but before helium fusion begions.
(D) a very massive main-sequence star.
(E) a white dwarf.
11/13/14 – slide 3
Discussion of exam questions: #24
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Which of the following characteristics of stars has the greatest
range in values?
Read: Chaps 19, 20
(A) surface temperature
(B) luminosity
(C) mass
(D) radius
(E) core temperature
11/13/14 – slide 4
Discussion of exam questions: #29
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Which cluster is 10 billion years old?
11/13/14 – slide 5
Discussion of exam questions: #41
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
What is the ultimate fate of an isolated white dwarf?
Read: Chaps 19, 20
(A) The electron degeneracy pressure will eventually
overwhelm gravity and the white dwarf will slowly
evaporate.
(B) As gravity overwhelms the electron degeneracy pressure,
it will explode as a supernova.
(C) It will cool down and become a cold black dwarf.
(D) As gravity overwhelms the electron degeneracy pressure,
it will explode as a nova.
(E) As gravity overwhelms the electron degeneracy pressure,
it will become a neutron star.
11/13/14 – slide 6
Galaxies!
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
11/13/14 – slide 7
Hubble Deep Field
Announcements
Exam questions
Galaxies!
Hubble Deep
Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Our deepest images of the universe show a great variety
of galaxies, some of them billions of light-years away
⊲
Read: Chaps 19, 20
11/13/14 – slide 8
Galaxies and Cosmology
A galaxys age, its distance,
and the age of the universe
are all closely related
The study of galaxies is
thus intimately connected
with cosmology—the study
of the structure and evolution of the universe
Read: Chaps 19, 20
11/13/14 – slide 9
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Hubble
Ultra
Deep
Field
11/13/14 – slide 10
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Hubble
Ultra
Deep
Field
11/13/14 – slide 10
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Hubble
Ultra
Deep
Field
11/13/14 – slide 10
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Hubble
Ultra
Deep
Field
11/13/14 – slide 10
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
11/13/14 – slide 11
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Disk Component: stars
of all ages, many gas
clouds
⊲
Read: Chaps 19, 20
Spheroidal
Component: bulge & halo, old
stars, few gas clouds
11/13/14 – slide 12
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Disk Component: stars of
all ages, many
gas clouds
⊲
Read: Chaps 19, 20
Spheroidal
Component:
bulge & halo,
old stars, few
gas clouds
11/13/14 – slide 13
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Disk Component: stars of
all ages, many
gas clouds
⊲
Read: Chaps 19, 20
Spheroidal
Component:
bulge & halo,
old stars, few
gas clouds
11/13/14 – slide 13
Three Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Disk Component: stars of
all ages, many
gas clouds
⊲
Read: Chaps 19, 20
Spheroidal
Component:
bulge & halo,
old stars, few
gas clouds
11/13/14 – slide 13
Thought question
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Why does ongoing star formation lead to a blue-white
appearance?
⊲
Read: Chaps 19, 20
(A) There aren’t any red or yellow stars
(B) Short-lived blue stars outshine others
(C) Gas in the disk scatters blue light
11/13/14 – slide 14
Thought question
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Why does ongoing star formation lead to a blue-white
appearance?
⊲
Read: Chaps 19, 20
(A) There aren’t any red or yellow stars
(B) Short-lived blue stars outshine others
(C) Gas in the disk scatters blue light
11/13/14 – slide 14
Other Types Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Barred Spiral Galaxy: Has a bar of stars across the bulge
Read: Chaps 19, 20
11/13/14 – slide 15
Other Types of Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Lenticular
Galaxy:
Has
a disk like a
spiral
galaxy
but much less
dusty gas (intermediate
between spiral
and elliptical)
11/13/14 – slide 16
Elliptical Galaxies
Elliptical Galaxy:
All
spheroidal
component,
virtually no disk
component
Read: Chaps 19, 20
11/13/14 – slide 17
Elliptical Galaxies
Elliptical Galaxy:
All
spheroidal
component,
virtually no disk
component
Red-yellow color
indicates older
star population
Read: Chaps 19, 20
11/13/14 – slide 17
Irregular Galaxies
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Large Magellanic Cloud
Read: Chaps 19, 20
11/13/14 – slide 18
Irregular Galaxies
Large Magellanic Cloud
Read: Chaps 19, 20
Blue-white color indicates ongoing
star formation
11/13/14 – slide 19
Hubble’s Galaxy Types
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Spheroid dominates
Read: Chaps 19, 20
Disk Dominates
11/13/14 – slide 20
How are galaxies grouped together?
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
11/13/14 – slide 21
Groups
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Spiral
galaxies
are often found in
groups of galaxies
⊲
Read: Chaps 19, 20
(up to a few dozen
galaxies)
11/13/14 – slide 22
Clusters
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Elliptical
galaxies
are
much
more common in
huge clusters of
galaxies
⊲
Read: Chaps 19, 20
(hundreds to thousands of galaxies)
11/13/14 – slide 23
Galaxies: summary
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies:
summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
How are the lives of galaxies connected with the history
of the universe?
⊲
Galaxies generally formed when the universe was
young and have aged along with the universe
What are the three major types of galaxies?
⊲
⊲
Spiral galaxies, elliptical galaxies, and irregular
galaxies
Spirals have both disk and spheroidal components;
ellipticals have no disk
How are galaxies grouped together?
⊲
⊲
Spiral galaxies tend to collect into groups of up to a
few dozen galaxies
Elliptical galaxies are more common in large clusters
containing hundreds to thousands of galaxies
11/13/14 – slide 24
Measuring distances to galaxies
Read: Chaps 19, 20
11/13/14 – slide 25
Measuring distances to galaxies
The Distance Ladder
Read: Chaps 19, 20
11/13/14 – slide 25
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Step 1: Measure the Solar System by RADAR to
determine the Astronomical Unit
⊲
Read: Chaps 19, 20
11/13/14 – slide 26
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Step 2: Determine distances of stars out to a
few hundred light-years
using parallax
⊲
Read: Chaps 19, 20
11/13/14 – slide 27
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Luminosity
passing
through each sphere is
the same
Area of sphere:
4π(radius)2
Divide luminosity by
area to get brightness
⊲
Read: Chaps 19, 20
11/13/14 – slide 28
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
The relationship between apparent brightness and luminosity
depends on distance:
Brightness =
Luminosity
4π(distance)2
We can determine a stars distance if we know its luminosity
and can measure its apparent brightness:
s
Luminosity
distance =
4πBrightness
A standard candle is an object whose luminosity we can
determine without measuring its distance
Read: Chaps 19, 20
11/13/14 – slide 29
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Step 3: Apparent
brightness of star
clusters main sequence tells us its
distance
⊲
Read: Chaps 19, 20
11/13/14 – slide 30
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance
Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Knowing a star clusters distance, we can determine the
luminosity of each type of star within it
Read: Chaps 19, 20
11/13/14 – slide 31
Thought question
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Which kind of stars are best for measuring large distances?
(A) High-luminosity stars
(B) Low-luminosity stars
⊲
Read: Chaps 19, 20
11/13/14 – slide 32
Thought question
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Which kind of stars are best for measuring large distances?
(A) High-luminosity stars
(B) Low-luminosity stars
⊲
Read: Chaps 19, 20
11/13/14 – slide 32
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Read: Chaps 19, 20
Step 4
Cepheid
variable
stars
are
very
luminous
Because the period
of a Cepheid variable star tells us its
luminosity, we can
use these stars as
standard candles
11/13/14 – slide 33
Cepheid Period-Luminosity relation
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
⊲
Cepheid variable stars with longer periods have greater
luminosities
Read: Chaps 19, 20
11/13/14 – slide 34
Type Ia Supernova
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia
Supernova
Tully-Fisher
Summary
⊲
White-dwarf supernovae can also be used as standard candles
Read: Chaps 19, 20
11/13/14 – slide 35
The Distance Ladder
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia
Supernova
Tully-Fisher
Summary
Step 5
Apparent brightness of
white-dwarf supernova
tells us the distance to
its galaxy
(up to 10 billion lightyears)
⊲
Read: Chaps 19, 20
11/13/14 – slide 36
Tully-Fisher relation
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
Entire galaxies can also
be used as standard candles because galaxy luminosity is related to rotation speed
⊲
Read: Chaps 19, 20
11/13/14 – slide 37
The Distance Ladder: Summary
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
We measure galaxy distances using
a chain of interdependent
techniques
⊲
Read: Chaps 19, 20
11/13/14 – slide 38
The Distance Ladder: Summary
Announcements
Exam questions
Galaxies!
Hubble Deep Field
Galaxies and
Cosmology
Three Types of
Galaxies
Thought question
Other types
Elliptical Galaxies
Irregular Galaxies
Hubble’s Galaxy
Types
Groups
Clusters
Galaxies: summary
Measuring distances
The Distance Ladder
Thought question
Cepheid PL
Type Ia Supernova
Tully-Fisher
Summary
The distance-measurement chain begins with parallax
measurements that build on radar ranging in our solar
system
Using parallax and the relationship between luminosity,
distance, and brightness, we can calibrate a series of
standard candles
We can measure distances greater than 10 billion light
years using white dwarf supernovae as standard candles
⊲
Read: Chaps 19, 20
11/13/14 – slide 39