No Slide Titlemctcteach.org/astronomy/Astronomy1110/PptsRaquel/20HubblesLaw_RJ.pdf• Astrophysics Lecture Due TODAY Dec. 3 (10 pts) Write report • Planetarium Due TODAY Dec. 3 (10

Study Points• What is a supercluster?

• How are galaxies distributed in the universe?

• What is Hubble’ Law? Can you apply it to stars? To galaxies in the Local

Group? To more distant galaxies?

• How do astronomers calculate distances to galaxies?

• What does Hubble’s Law tell us about the origin of the universe?

• When we see objects like stars or galaxies in pictures, are we seeing them

as they look now or in the past? Why?

• Is the red shift caused by galaxies moving through space or by space-time

expanding?

• Is the universe expanding, contracting or neither? How do we know? Is the

universe cooling?

• Discuss the raisin bread model or balloon model to explain why we do not

have to be at the center of the universe.

• What is the name of the theory of how the universe evolved?

• Give a brief timeline for the formation of the universe (BB, first stars, our

galaxy, our solar system).

• How old is our universe? How old is our solar system?

Hubble’s Law• Review

– Cluster of Galaxies

• The Local Group

• Superclusters

• Hubble’s Law

• Red Shift of galaxies

• Big Bang model

Clusters of Galaxies

Galaxy cluster mass ~160 trillion times the mass of the sun

http://www.spacetelescope.org/news/heic1416/

http://www.spacetelescope.org/news/heic1416/

The Local Group• Group of galaxies including Milky Way

Virgo Supercluster

• Milky Way is part

of the Virgo

Supercluster

• Supercluster*

– Cluster of

galaxy clusters

http://heasarc.nasa.gov/docs/cosmic/local_supercluster_info.html

http://heasarc.nasa.gov/docs/cosmic/local_supercluster_info.html

Neigboring Superclusterswithin 1 billion light years

Every dot is a galaxy

http://www.atlasoftheuniverse.com/superc.html

http://www.atlasoftheuniverse.com/superc.html

Laniakea SuperclusterNamed & Discovered in 2014

Home to the Milky Way & 100,000 Galaxies

Laniakea Supercluster in yellow

Superclusters:

• Virgo (MW)

• Hydra

• Centaurus

• Pavo-Indus

More Info here:

https://www.forbes.com/sites/startswithabang/2017/02/24/cosmic-superclusters-the-

universes-largest-structures-dont-actually-exist/#1ccf468e15c1

Picture: http://www.atlasoftheuniverse.com/superc.html

https://www.forbes.com/sites/startswithabang/2017/02/24/cosmic-superclusters-the-universes-largest-structures-dont-actually-exist/#1ccf468e15c1http://www.atlasoftheuniverse.com/superc.html

Superclusters

• How are galaxies distributed?

– In great strings and voids*

• What does the distribution look like to you?

Superclusters

• How are galaxies distributed?

– In great strings and voids*

• What does the distribution look like to you?

– Edges of soap bubbles

– Holes of Swiss cheese

Watch & fly through galaxies with the Sloan Digital Sky Survey

(1:49): https://www.youtube.com/watch?v=08LBltePDZw

https://www.youtube.com/watch?v=08LBltePDZw

Superclusters• Laniakea: Our home supercluster• Watch Video by Nature, 2014 (4:10)

https://www.youtube.com/watch?v=rENyyRwxpHo


Doppler Effect

• What does the red shift or blue shift tell you?

Doppler Effect

• Red shift / blue shift tells you…

Direction of motion (away/toward) & speed

• Bigger shift means …• For all cases like galaxies, stars, cars…

– For light and sound

faster

FOR GALAXIES ONLY

(not stars or cars)

Edwin Hubble & Hubble’s Law• Measured distance, D, to galaxies

• Recall: Type of star gave L, then

• B = kL/D2

• Measured red shift of those galaxies to get their speeds, v.

Edwin Hubble

1929

Edwin Hubble, 1929

Graphed v vs. D

Speed, v Distance, D

V

speed

D

Distance

*

*

**

**

*

Straight Line!!

Hubble’s Law

V

speed

D

Distance

*

*

**

**

*

Distant galaxies

move faster.*

Hubble’s Law

V

D

**

*** *

* v = HD

Distant galaxies move faster*

Hubble’s Law

V

D

**

*** *

*

Implications?

For galaxies, the

speed gives you the

distance!*

v = HD

H = Hubble’s

Constant (slope)

Hubble’s Law

V

D

**

*** *

*

*So, today, to measure

distance to a galaxy …

Measure the Red Shift.

That gives the speed.

Then use Hubble’s Law ( v = HD ) to get

distance.*

(Don’t try this with stars or cars! Only for

galaxies.)*

Hubble’s Law

V

D

**

* ** *

*

All galaxies

(outside the Local Group)

show a Red Shift.*

Distant galaxies move

faster* v = HD

Hubble’s Law

V

D

**

*** *

*

Implications? What does

this mean?

All galaxies Red Shifted*

All galaxies moving away

from us!* (outside Local Group)

Universe is expanding!*

This expansion is from

the expansion of space-

time.*

Hubble’s Law

V

D

**

* ** *

*

But if universe is

expanding, what was

it like yesterday?

Smaller!*

And billions of years ago??

Even smaller!

Hubble’s Law

V

D

**

* ** *

*

So at one point it

must have been very

small.

Hence the name…

BIG BANG

V

D

**

* ** *

*

Bad Name (misnamed)

Was not BIG

Did not BANG

BIG BANG

More descriptive name

Great Unfolding

Or

Big Stretch

Warning: The Astronomy General has

determined that this image may be hazardous

to your misconceptions.

BIG

BANG

Big Bang • Universe (space and time)

• Springs into existence (tiny)

• About 14 billion years ago

• Expanding or Shrinking?




• Expanding ever since

Science states that is the universe is expanding,

and it is cooling as it expands. The universe

started hot and has been cooling ever since.

The expansion should be slowing down due to

the force of gravity pulling everything inward.




• Expanding, cooling ever since

• Expansion slowing due to gravity






What is the rate of expansion now?

Is the rate…

a) Slowing down

b) Speeding up

c) Not changing






What is the rate of expansion now? Is the

rate…

a) Slowing down due to gravity Old Model

b) Speeding up

c) Not changing






What is the rate of expansion now? Is the

rate…

a) Slowing down due to gravity Old Model

b) Speeding up Current Model*

c) Not changing




• Expanding, cooling ever since* (started hot)

• Expansion slowing due to gravity (first ~9 Byr)

• Expansion speeding up due to dark energy

(last ~5 Byr) & currently

Rate of expansion is speeding up!*

The cause is named Dark Energy.*(more on dark energy in next lecture)

Expansion Rate is about 14 (mi/sec)/million light years

Universe Expansion

Acceleration Due to Dark Energy

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

Tim

e

(~1

4 b

illi

on

ye

ars

)T

ime

(~1

4 b

illi

on

ye

ars

)

~9 Byrs

~5 Byrs

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

After accounting for the universe expansion:

Galaxies moving away from us are in red, those moving toward us in blue (Nature Video, based on Tully et al 2014)


Why do distant galaxies move

faster?

Remember that space-time itself is

expanding!

Galaxies are NOT moving much

through space but space-time is

expanding, dragging galaxies with it.

Why do distant galaxies move faster?

Think of a rubber map and stretch it.

Why do distant galaxies move faster?

Think of a rubber map and stretch it.

• Example: Triple size (3X) in one hour.

• A city 10 miles away will then be 30 miles away– moved 20 mi/h

• A city 100 miles away will then be 300 miles away. – moved 200 mi/h

• When the map stretches, more distant city moves

faster.

Similarly, as space-time expands, more distant

galaxies move faster.

Universe Expansion ⇒ Distant objects move faster

Universe

Doesn’t seeing a Red Shift of ALL

galaxies imply that we are at the center

of the universe? (all moving away?)

NO!

But why?

Raisin Bread

Model

Everything can appear to move

away from you, no matter where

you are located.*

Balloon Expanding

• Demo

• One piece of balloon sees all other pieces moving away

• That piece does not need to be at the center

You can read more here about why we can’t find the center of the universe.

http://oneminuteastronomer.com/6949/where-is-the-center-of-the-universe/

http://oneminuteastronomer.com/6949/where-is-the-center-of-the-universe/

Doesn’t seeing a Red Shift of ALL

galaxies imply that we are at the center

of the universe? (all moving away?)

NO!

Expansion

You see all other parts moving away

You are not at center

Where is the center?

I see a galaxy

10 BLY away…

…as it was 10

Byrs ago…

…when the

universe was

smaller…

…so I’m

looking back

toward the

center.

…so I’m

looking out

toward the

center.

Yes, so I am

looking out

toward the

center too.

We are all

looking out

toward the

center

Center is

here

Center is

hereCenter is

here

Center is

here

Center is

hereCenter is

here

Center is

here

Center is

here

An ant on a balloon has no way to

know where the center is.*

We can’t find the center of the

universe!

And we don’t think a center exists!*

http://scienceblogs.com/startswithabang/20

09/07/31/the-size-of-the-universe-a-har/

http://staff.on.br/jlkm/astron2e/AT_MEDIA/

CH27/CHAP27AT.HTM

http://scienceblogs.com/startswithabang/2009/07/31/the-size-of-the-universe-a-har/http://staff.on.br/jlkm/astron2e/AT_MEDIA/CH27/CHAP27AT.HTM

Big Bang and the

Evolution of the Universe

http://www.space.com/25075-cosmic-inflation-universe-expansion-big-bang-infographic.html

http://www.space.com/25075-cosmic-inflation-universe-expansion-big-bang-infographic.html

Big Bang and the

Evolution of the Universe

How the universe evolved and changed

after it started.*

In the beginning??? What happened

next?

• Rough timeline of events today

• Evidence (next lecture)

Very Rough Cosmic Timeline

Big BangNow

Stuff

Happenst > 014 billion

years later

Milky

Way

Solar

system and

Earth

H, He

First

stars First

human

s

Galaxies collide

and grow

First

galaxies

Cosmic CalendarFrom The Dragons of Eden 1977

& Cosmos TV Series - Carl Sagan

Updated in Cosmos: A Spacetime Odyssey episode 1

Jan Big BangH and He, First stars,

First galaxies

FebMilky Way Galaxy

Mar

Apr MayMilky Way Galaxy

Jun

Jul Aug SepSolar system, Earth

Life on Earth

OctOldest fossils

Nov DecFirst cells with nuclei

1

O2

2 3 4 5

Mars

channels

6 7

8 9 10 11 12 13 14

15 16

Worms

17 18

Plankton

19

Fish

20 21

Insects

22

Amphibians

23

Trees

24

Dinosaurs

25 26

Mammals

27

Birds

28

Flowers

29

Primates

30

Hominids

31

Humans

December

December 3111:59:37 p.m. Agriculture

11:59:45 p.m. The Wheel

11:59:56 p.m. Ptolemy – astronomy

11:59:58 p.m. Mayan civilization; Byzantine empire

11:59:59 p.m. Renaissance; experimental method in science; the telescope

Now

http://www.astrosociety.org/edu/astro/act2/H2_Cosmic_Calendar.pdf

About how old is our universe?*

About how old is our universe?*

14 billion years*

About how old is our Milky Way Galaxy?

About how old is our Milky Way Galaxy?

13 billion years

About how old is our solar system?*

About how old is our solar system?*

5 billion years*

(same age as our Sun)*

Homework & Updates• Keep up with Study Points

• D2L Quiz 9-12 available; Quizzes 9-13 for Test 3

• Optional – watch:• The Big Bang, Cosmology part 1: Crash Course Astronomy #42

• A Brief History of the Universe: Crash Course Astronomy #44

• Observations:• Astrophysics Lecture Due TODAY Dec. 3 (10 pts) Write report• Planetarium Due TODAY Dec. 3 (10 pts) Go to a planetarium show• Astronomy News Evalution Due Dec. 10 (20 pts) Evaluate astronomy news• Sunset – Part 2 Due Dec. 10 (10 points) Take 2nd picture of sunset in same place

• Take picture about 4pm; sunsets about 4:40pm• Stargazing Due Dec. 17 (20 pts) Go stargazing & write report• Telescope Due Dec. 17 (20 pts) Look through a telescope

• Look at calendar options & weather• Moon Craters Due Dec. 17 (10 pts) Look at magnified moon craters

• Borrow binoculars from Lab room

• Pick up lab notebooks and test today• Let Raquel know if you want to take the optional Lab Test 2 on Dec. 10 or 12

• Grade calculator on website to try out different grades.

Optional – watch:•The Big Bang, Cosmology part 1: Crash Course Astronomy #42

•A Brief History of the Universe: Crash Course Astronomy #44

https://www.pbs.org/video/crash-course-astronomy-42/https://www.pbs.org/video/crash-course-astronomy-44/http://mctcteach.org/astronomy/Astronomy1110/Handouts/AstrophysicsLecture.pdfhttp://mctcteach.org/astronomy/Astronomy1110/Handouts/Planetarium.pdfhttp://mctcteach.org/astronomy/Astronomy1110/HandoutsRaquel/AstroNewsEvalRaquel.pdfhttp://mctcteach.org/astronomy/Astronomy1110/Handouts/SunsetFALLPart2.pdfhttp://mctcteach.org/astronomy/Astronomy1110/HandoutsRaquel/StargazeRJ.pdfhttp://mctcteach.org/astronomy/Astronomy1110/HandoutsRaquel/TelescopeRJ.pdfhttp://mctcteach.org/astronomy/Astronomy1110/Handouts/Mooncraters.pdfhttps://www.pbs.org/video/crash-course-astronomy-42/https://www.pbs.org/video/crash-course-astronomy-44/

Calendar Summary• Tuesday, 11/26: No lecture or lab. Work on observations.

• Tuesday, 12/3: Hubble’s Law & Galaxies & pick up lab

notebooks in lecture

• Thursday, 12/5: Big Bang

• Tuesday, 12/10: Life in the Universe (optional Lab Test 2)

• Thursday, 12/12: Test 3 (60 multiple choice questions)– Based on last 8 lectures & 5 D2L quizzes 9-13

– Some questions from D2L quizzes

– Bring pencil, no calculator needed

– Optional Lab Test 2 during lab time

• Tuesday, 12/17: Final Test today & handback Test 3– Based on all 23 lectures & 13 D2L quizzes (the whole semester)

– Many questions from D2L quizzes

– Bring pencil & calculator if you have one (some in classroom for you)

– Remember lowest of 4 tests is dropped (Test 1, 2, 3, & Final).

– If you took 3 previous tests and are happy with your grade, then you

don’t have to take the Final Test. If you missed a previous test, you

must take the Final Test. If you are trying to increase your grade, take

the final to hopefully drop a different test. No Astronomy on 12/19.

Documents

No Slide Titlemctcteach.org/astronomy/Astronomy1110/PptsRaquel/20HubblesLaw_RJ.pdf• Astrophysics Lecture Due TODAY Dec. 3 (10 pts) Write report • Planetarium Due TODAY Dec. 3 (10