Martin D. Weinberg UMass Astronomy astron100...

Read: Chaps 19, 20 11/13/14 – slide 1

A100–Exploring the Universe: Discovering Galaxies

Martin D. Weinberg

UMass Astronomy

astron100-mdw@courses.umass.edu

November 13, 2014

Announcements

⊲ Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 2

Exam #2 questions returned after class today

Solutions posted on the website in the “exams” tab. See

http://courses.umass.edu/astron100-mdw

Announcements

⊲ Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 2

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?

Announcements

⊲ Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 2

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?

Discussion of exam questions: #39

Announcements

⊲ Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 3

Degeneracy pressure is the source of the pressure that stops

the crush of gravity in all of the following except

(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.

Discussion of exam questions: #24

Announcements

⊲ Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 4

Which of the following characteristics of stars has the greatest

range in values?

(A) surface temperature

(B) luminosity

(C) mass

(D) radius

(E) core temperature

Discussion of exam questions: #29

Announcements

⊲ Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 5

Which cluster is 10 billion years old?

Discussion of exam questions: #41

Announcements

⊲ Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 6

What is the ultimate fate of an isolated white dwarf?

(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.

Galaxies!

Announcements

Exam questions

⊲ Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 DeepField

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 8

Our deepest images of the universe show a great variety

of galaxies, some of them billions of light-years away

Galaxies and Cosmology

Read: Chaps 19, 20 11/13/14 – slide 9

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 evolu-

tion of the universe

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 10

Hub-

ble

Ultra

Deep

Field

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 10

Hub-

ble

Ultra

Deep

Field

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 10

Hub-

ble

Ultra

Deep

Field

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 10

Hub-

ble

Ultra

Deep

Field

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 12

Disk Component: stars

of all ages, many gas

clouds

Spheroidal Compo-

nent: bulge & halo, old

stars, few gas clouds

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 13

Disk Compo-

nent: stars of

all ages, many

gas clouds

Spheroidal

Component:

bulge & halo,

old stars, few

gas clouds

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 13

Disk Compo-

nent: stars of

all ages, many

gas clouds

Spheroidal

Component:

bulge & halo,

old stars, few

gas clouds

Three Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

⊲Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 13

Disk Compo-

nent: stars of

all ages, many

gas clouds

Spheroidal

Component:

bulge & halo,

old stars, few

gas clouds

Thought question

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

⊲ Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 14

Why does ongoing star formation lead to a blue-white

appearance?

(A) There aren’t any red or yellow stars

(B) Short-lived blue stars outshine others

(C) Gas in the disk scatters blue light

Thought question

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

⊲ Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 14

Why does ongoing star formation lead to a blue-white

appearance?

(A) There aren’t any red or yellow stars

(B) Short-lived blue stars outshine others

(C) Gas in the disk scatters blue light

Other Types Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

⊲ Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 15

Barred Spiral Galaxy: Has a bar of stars across the bulge

Other Types of Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

⊲ Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 16

Lenticular

Galaxy: Has

a disk like a

spiral galaxy

but much less

dusty gas (in-

termediate

between spiral

and elliptical)

Elliptical Galaxies

Read: Chaps 19, 20 11/13/14 – slide 17

Elliptical Galaxy:

All spheroidal

component, vir-

tually no disk

component

Elliptical Galaxies

Read: Chaps 19, 20 11/13/14 – slide 17

Elliptical Galaxy:

All spheroidal

component, vir-

tually no disk

component

Red-yellow color

indicates older

star population

Irregular Galaxies

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

⊲ Irregular Galaxies

Hubble’s GalaxyTypes

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 18

Large Magellanic Cloud

Irregular Galaxies

Read: Chaps 19, 20 11/13/14 – slide 19

Large Magellanic CloudBlue-white color indicates ongoing

star formation

Hubble’s Galaxy Types

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

⊲Hubble’s GalaxyTypes

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 20

Spheroid dominates Disk Dominates

How are galaxies grouped together?

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

⊲Hubble’s GalaxyTypes

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 andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

⊲ 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 22

Spiral galaxies

are often found in

groups of galaxies

(up to a few dozen

galaxies)

Clusters

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 23

Elliptical galax-

ies are much

more common in

huge clusters of

galaxies

(hundreds to thou-

sands of galaxies)

Galaxies: summary

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 24

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

Measuring distances to galaxies

Read: Chaps 19, 20 11/13/14 – slide 25

Measuring distances to galaxies

Read: Chaps 19, 20 11/13/14 – slide 25

The Distance Ladder

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 26

Step 1: Measure the So-

lar System by RADAR to

determine the Astronom-

ical Unit

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 27

Step 2: Determine dis-

tances of stars out to a

few hundred light-years

using parallax

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 28

Luminosity passing

through each sphere is

the same

Area of sphere:

4π(radius)2

Divide luminosity by

area to get brightness

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 29

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:

distance =

√

Luminosity

4πBrightness

A standard candle is an object whose luminosity we can

determine without measuring its distance

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 30

Step 3: Apparent

brightness of star

clusters main se-

quence tells us its

distance

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

⊲The DistanceLadder

Thought question

Cepheid PL

Type Ia Supernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 31

Knowing a star clusters distance, we can determine the

luminosity of each type of star within it

Thought question

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 32

Which kind of stars are best for measuring large distances?

(A) High-luminosity stars

(B) Low-luminosity stars

Thought question

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 32

Which kind of stars are best for measuring large distances?

(A) High-luminosity stars

(B) Low-luminosity stars

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 33

Step 4

Cepheid variable

stars are very

luminous

Because the period

of a Cepheid vari-

able star tells us its

luminosity, we can

use these stars as

standard candles

Cepheid Period-Luminosity relation

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 34

Cepheid variable stars with longer periods have greater

luminosities

Type Ia Supernova

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

The Distance Ladder

Thought question

Cepheid PL

⊲Type IaSupernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 35

White-dwarf supernovae can also be used as standard candles

The Distance Ladder

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

Groups

Clusters

Galaxies: summary

Measuring distances

The Distance Ladder

Thought question

Cepheid PL

⊲Type IaSupernova

Tully-Fisher

Summary

Read: Chaps 19, 20 11/13/14 – slide 36

Step 5

Apparent brightness of

white-dwarf supernova

tells us the distance to

its galaxy

(up to 10 billion light-

years)

Tully-Fisher relation

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 37

Entire galaxies can also

be used as standard can-

dles because galaxy lu-

minosity is related to ro-

tation speed

The Distance Ladder: Summary

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 38

We measure galaxy distances using

a chain of interdependent

techniques

The Distance Ladder: Summary

Announcements

Exam questions

Galaxies!

Hubble Deep Field

Galaxies andCosmology

Three Types ofGalaxies

Thought question

Other types

Elliptical Galaxies

Irregular Galaxies

Hubble’s GalaxyTypes

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 39

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