Prof. Geoff Marcy

Jupiter and Europa

Saturn and Enceladus

Textbook: The Cosmic Perspective

Bennett et al.

Order from Bookstore (takes a few days) to get kit for homework:

MasteringAstronomywww.masteringastronomy.com Course ID: THEPLANETSFALL2012

Or get a used book, and purchase MasteringAstronomy online

Reading this week and next week: Chapters 1 and 2 “Our place in the Universe “ & “Discovering the Sky”

Homework: Due every Friday at 6pm Chapter 1 and Chapter 2 Assignments: due Friday Aug 31 at 6pm Tuesday Sept. 4 @ 6pm 5% off for each wrong try. 2% for a hint.

12 Discussion Sections • All start this week. • Review, Clarification, Homework Help. Sign up on Telebears

101 Wed 9-10A, 265 McCone Hall: Ben Legg102 Wed 1-2P, 264 Evans Hall: Lea Hirsch103 Wed 2-3P, 264 Evans Hall: Tess McEnulty 104 Wed 3-4P, 241 Cory Hall: Tess McEnulty105 Th 2-3P, 264 Evans Hall: Lea Hirsch106 Tu 2-3P, 264 Evans Hall: Tess McEnulty107 Th 11-12P, 264 Evans Hall: Ryan Turner108 Tu 11-12P, 264 Evans Hall: Ryan Turner 109 Tu 12-1P, 264 Evans Hall: Drummond Fielding110 Th 12-1P, 264 Evans Hall: Lea Hirsch111 W 11-12P, 264 Evans Hall: Ben Legg112 Wed 12-1P, 264 Evans Hall: Drummond Fielding

Observing Project #1Two choices

B) Sketch where the Sun sets, relative to buildings. Wait 4-10 days. Sketch where the Sun sets again. Turn in both sketches, with time and date of observation. Write three sentences about any change in the position of sunset. Did it change? What direction? By how many degrees (approx.)? (The sun has an angular size of 0.5 degrees in diameter.)

Due in class, Thursday Sept. 61 page maximum; Handwritten is fine.

A) Chart the position and shape of the moon. Sketch where the moon is located relative to nearby buildings. Also sketch the shape of the moon. Mark which direction is south. Note the time and day on the sketch. Wait 2-5 days, and do it again. (Hint: the moon is up now from 8pm-2am)

Turn in both sketches, with time and date of observation. Write three to four sentences about any change you saw in the position or shape.

Course material on bSpace: http://bspace.berkeley.edu

• Syllabus

• Lecture slides

• Assignments: reading, homework, observing projects

• Course information

Last Time ::

The Solar SystemInner Solar System Outer Solar System

The Solar System:Sun and 8 Planets

Moons, Rings, Asteroids, Comets, and Dust

Milky Way Galaxy

You Are Here

200 Billion StarsPhoto taken from Earth

Our Sun moves relative to the other stars in the local Solar neighborhood.

Our Sun and the stars orbit around the center of the Milky Way Galaxy every 230 million years.

Our Milky Way Galaxy

Spiral Galaxies

Elliptical Galaxies

Irregular Galaxies

The Galactic Neighborhood

100,000 Light YearsThe ``Local Group”of Galaxies

The ``Local Group’’of Galaxies

And outward…10 Million Light Years

All matter and energy

> 100 Billion Galaxies

The Universe:

Astronomical Numbers

Best to use Exponential Notation

Exponential notation is handy:

10N x 10M = 10(N+M)

103 = 1000 Thousand106 = 1,000,000 Million109 = 1,000,000,000 Billion1012 = 1,000,000,000,000 Trillion

Also: 10–3 = 1/1000 = 0.001

103 x 106 = 109 thousand million billion

Example:

B

How many stars in our visible Universe?

A. 1012 (1 million million)

B. 1018 (1 billion billion)

C. 1022

D. infinite

Interactive QuizB

A. 1012 (1 million million)

B. 1018 (1 billion billion)

C. 1022

D. infinite

Interactive Quiz

Number of Stars in a galaxy: ~100 billion = 1011

Number of galaxies in Universe: 100 billion = 1011

B

How many stars in our visible Universe?

There are 1011 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.

Richard Feynman

B

Federal Deficit each Year

In 2012, the National Debt is $15.9 Trillion

U.S. Population = 311 x 106 people

$15.9 x 1012 / 3.11 x 108 = $5 x 104

= $50,000 per person

= $15.9 x 1012

Your Personal Debt:

B

B

Population of US: 300 millionCost per person: $787x109 / 3x108 = $2623

Distance, time and number :

Radius of our Galaxy:6,000,000,000,000,000,000 m =

Radius of a Hydrogen atom:0.00000000005 m =

Time for one vibration of an oxygen molecule, O2:

0.00000000000001 s =

Age of the Universe:430,000,000,000,000,000 s =

Scientific notation: 6 x 1018 m

1 x 10–14 s

4.3 x 1017 s = 13.6 billion years

0.5 x 10–10 m

B

SI (Systeme International) Units

Base units: 1 meter (m) length ~ 3.3 ft

1 kilogram (kg) mass ~ 2.2 lb

1 second (s) time

B

SI (Systeme International) Units

Base units: 1 meter (m) length

1 kilogram (kg) mass

1 second (s) time

MKS System of units and measure

Sometimes easier to derive other units from these:

km, g, ms, µs, … km = 103 m kilo

g = 10-3 kg kilo

ms = 10-3 s milli

µs = 10-6 s micro

B

UNITS ARE IMPORTANT!!!

Mars Climate Orbiter: Launch: 11 Dec. 1998

Orbit insertion: 23 Sep. 1999

Followed by: Loss of Communication

WHY?

Failed to convert from English units (inches, feet, pounds) to Metric units (MKS) $Billion error

B

Speed of Light

and Light-travel time:

C = 3 x 108 m/sec

= 3 x 105 km/sec = 300,000 km/sec

= 0.3 m/ns (1 ns = 10-9 s)

Light Year = 9 trillion km = 6 trillion milesLight HourLight Minutes are unit of Distance:

How far Light Travels in that interval of time1 light second = 3 x 105 km1 light ns = 30 cm ≈ 1 foot

B

How long does it take the sun’s light to reach the Earth?

Distance d = 1 AU = 1.5x1011m

Speed of light c = 3x108 m/s

Time

€

t =d

v=

1.5 ×1011m

3 ×108 m /s= 0.5 ×103 s ≈ 8 min

B

Driving Curiosity Rover on Mars

• How long does it take to communicate with Curiosity ?

B

How long does it take for radio waves (light) to reach

Mars?

A. Less than 1 second

B. 1 minute

C. 10 minutes

D. 1 hour

Interactive QuizB

How long does it take for radio waves (light) to reach Mars?

A. Less than 1 second

B. 1 minute

C. 10 minutes

D. 1 hour

Interactive QuizB

Earth-Mars distance: between 55 and 400 million km.

tmin = dmin/v = 5.5×107 km / (3×105 km/s ) =1.8×102s= 3 minutes

tmax = dmax/v = 4.0×108 km / (3×105 km/s ) =1.3×103s= 22 minutes

A Scaled Model of the Solar System

10 Billion x SmallerSun’s diameter: 14 x 1010 cm

Reduce by 1010: 14 cm

Earth diameter: 13000 km 0.13 cm

Jupiter’s diameter: 150,000 km 1.5 cm

Earth’s distance from Sun: 1 “Astronomical Unit” = 1 “AU”

= 1.5 x 108 km1 AU ?? cm

Ans: 1500 cm = 15 meters

14cm

1010 Scaled Down

“Sun”

A. 1.5 cmB. 15 cmC. 150 cmD. 1500 cm

How large is the Solar System?• Let’s view it to scale

– Say the Sun is the size of a large grapefruit, 14 cm (6 inches) - then:

G

Planet Dist (AU) Scaled Dist (m) Where?

Mercury 0.4 6 6 rows back

Venus 0.7 10 10 rows

Earth 1.0 15 15 rows

Mars 1.5 22 22 rows

Jupiter 5 75 3/4 football field away

Saturn 10 150 1.5 football field away

Uranus 20 300 Sproul Plaza

Neptune 30 450 Bancroft Ave

Pluto 50 750 Durant Ave

Oort Cloud 50,000 5 x 105 Oakland

.

100 m

Saturn

oUranus o

Neptune o

Jupiter

o

You Are Here:Earth’s Orbit

G

.

How Far is the Nearest Star?Alpha Centauri d = 4 light years

= 4 x 1016 m

Scales to:4 x 106 m(~ 3000 mi)

G

Grapefruit-sizedSun in Berkeley

Nearest Grapefruit:

In Washington D.C.

Powers of Ten“Cosmic Voyage”

The Movie

G

How to deal with very large & small numbers

•Develop a useful arithmeticExponential notation; convert between units

•Visualize using a sequence of images (movie)Use different sequences

•Visualize by way of a scale modelTry different models

G

A Universe in motion• Contrary to our perception, we are not “sitting still.”• We are moving with the Earth.

– and not just in one direction

The Earth rotates around it’s axis once every day.

G

The Earth orbits around the Sun once every year.

The Earth’s axis is tilted

by 23.5º !

G

Looking back in time• Light, although fast, travels at a finite speed.• It takes:

– 8 minutes to reach us from the Sun– 8 years to reach us from Sirius (8 light-years away)– 1,500 years to reach us from the Orion Nebula

• The farther out we look into the Universe, the farther back in time we see!

B

The Origin of the Universe

Most of the atoms in our bodies were created in the core of a star.

(1) The two simplest atoms, H and He, were created during the Big Bang.

B

(2) More complex atoms were created in stars.

(3) When the star dies, chemical elements are expelled into space, to form new stars and planets!

• Galaxies appear to be moving away from us.• The farther away they are, the faster they are moving.• Space itself is expanding

pace itself expands.

How old is the Universe?

• The Cosmic Calendar– if the entire age of

the Universe were one calendar year

– one month would be approximately 1 billion real years

B

The Universe in a Day 

Look at the entire history of the Universe as though it took place in a single day. The present is at the stroke of midnight at the end of that day. Since it is about 13.5 billion years old, each hour will be ~0.5 billion years. A million years takes only a little over 7 seconds.

 

The Big Bang (a dense, hot explosion) and the formation of H and He all take place in the first nanosecond. The Universe becomes transparent in about 2 seconds. The first stars and galaxies appear after about 2am.

Our Galaxy forms at 4am. Generations of stars are born and die.

 

B

The Universe in a Day 

The Solar System does not form until 3pm. The first life (bacterial) appears on the Earth by 4pm. Our atmosphere begins to have free oxygen at 7 or 8 pm, and this promotes the development of creatures which can move more aggressively and eat each other. Life does not begin to take on complex forms (multicellular) until 10:45pm. It moves onto land at 11:10. The dinosaurs appear at about 11:40, and become extinct at 11:52. Pre-human primates appear at around 14 seconds before midnight, and all of recorded history occurs in the last 70 milliseconds.

 

Looking to the future, we can expect the Universe of stars to go on for at least another millennium (using the same time compression factor). After that, there are other ages of the Universe (not dominated by stars), which grow colder and more bizarre, and take place on astronomical timescales…

B

What is the Earth’s velocity about the Sun?

Radius of Orbit (1 AU): 150 x 106 km

Circumference: 2 π x radius

Distance around the Sun that the Earth travels:

2 π x (1.5 x 108 km) = 9 x 1011 m

Earth orbits the Sun once a year:

1 yr = 3 x 107 s

Velocity = Distance/Time = 9 x 1011 m / 3 x 107 s

= 3 x 104 m/s = 30 km/s

110,000 km/hr or 75,000 miles/hr!

B