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Astronomy C12, Earth & Planetary Science C12, Letters & Science C70 The Planets

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## Astronomy C12, Earth & Planetary Science C12, Letters & Science C70 The Planets

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### Homework: 50% of your grade

### Homework:

### How many stars in our visible Universe?

Astronomy C12, Earth & Planetary Science C12, Letters & Science C70

The Planets

Prof. Michael Manga

Prof. Geoff Marcy

Dione

in front of

Saturn and

its Ring

Tu, Th 11-12:30 am

100 Lewis

Geoff Marcy 417 Campbell Hall gmarcy@berkeley.edu

Michael Manga 173 McCone Hall manga@seismo.berkeley.edu

Departments of Astronomy, Earth & Planetary Science

GSIs:

Linda Strubbe linda@astron

Nicholas McConnell nmcc@astro

Arianna Gleason aegleason@lbl.gov

Karrie Weaver karrie@eps

8 Discussion Sections 1 hr each (Start Next Week)

Review, Clarification, Homework Help

Sign up for Section on Telebears

The Solar System:

The Cosmic Perspective

Bennett et al. (2006) 4th Edition (not 3rd)

- Web Site on bspace:http://bspace.berkeley.edu
- Syllabus, Schedule & Lecture Figures (no animation)
- Assignments: Reading, Homework, Observing Project
- Class Information

12 assignments during semester

Most questions from your text

The Astronomy Learning Center (TALC):

264 Evans Time: TBA

First homework set available Friday

Due by Friday Feb 2

Turn in HW by Friday at noon:

Box labeled Astro/EPS 12 in the basement of Campbell Hall.

You are encouraged to work together, but MUST turn in your own work, in your own words

The graders can recognize copying, and answers found with Google

Refer to the Berkeley Code of Student conduct if you are unclear about what constitutes cheating or plagiarism

- No discussion sections this week
- Read Ch 1 of the text this week; Ch 2 by next
- First Homework Assignment: posted Friday.
- No Clickers

The Solar System

The Solar System:Sun and 8 PlanetsMoons, Asteroids, Comets, and Dust

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.

And outward…

10 Million Light Years

Exponential notation is handy:

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

Astronomical Numbers

Best to use Exponential Notation

103 = 1000 Thousand

106 = 1,000,000 Million

109 = 1,000,000,000 Billion

Also:

10–3 = 1/1000

= 0.001

Example:

103 x 106 = 109

thousand million billion

106 (1 million)

1012 (1 million million

1018 (1 billion billion)

1022

infinite

$7.6 Trillion

Federal Debt

= $7.6 x 1012

U.S. Population = 300 x 106

Calculate Your Debt:

$7.6 x 1012 / 3 x 108 =

$2.5 x 104

Trillions of Dollars

$25,000 per person

02 03 04 05

Debt Total

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:

470,000,000,000,000,000 s =

Scientific notation:

6 x 1018 m

0.5 x 10–10 m

1 x 10–14 s

4.7 x 1017 s = 14 billion years

SI (Systeme International) Units

- Base units: 1 meter (m) length ~ 3.3 ft
- 1 kilogram (kg) mass ~ 2.2 lb
- 1 second (s) time
- MKS System of units and measure

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

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)

3 x 108 m/sec

= 3 x 105 km/sec

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

Light Year = 9 trillion km = 6 trillion miles

Light Hour

Light Minutes are unit of Distance:

How far Light Travels in that interval of time

1 light second = 3 x 105 km

1 light ns = 30 cm ≈ 1 foot

Driving the Mars Exploration Rovers (MER)

- How long does it take to communicate with the rovers?

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

- Less than 1 second
- 10 seconds
- 5 minutes
- 1 day
- 1 year

How to deal with very large & small numbers

- Develop a useful arithmetic
- Exponential notation; convert between units
- Visualize using a sequence of images (movie)
- Use different sequences
- Visualize by way of a scale model
- Try different models

A Scaled Model of the Solar System

10 Billion x Smaller

Sun’s diameter: 14 x 1010 cm (~ 106 miles)

Scale 1010: 14 cm

Earth diameter: 1.3 x 104 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 km

1010

Scaled Down

“Sun”

14cm

1 AU ?? cm

0.15 cm

1.5 cm

15 cm

150 cm

1500 cm

Ans: 1500 cm = 15 meters

How large is the Solar System?

- Let’s view it to scale
- say the Sun is the size of a large grapefruit, 15 cm (6 inches)

- then:

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

How Far is the Nearest Star?

Alpha Centauri

d = 4 light years

= 4 x1016 m

Scales to:

4 x 106 m

(~ 3000 mi)

Grapefruit-sized

Sun in Berkeley

Nearest Grapefruit:

In Washington D.C.

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

- What does our solar system look like when viewed to scale?
- How far away are the stars?
- How do human time scales compare to the age of the Universe?

- Solar System Resides within our Milky Way Galaxy
- Ranges of distances and time are huge.
- Exponential notation and models are a real Help!
- Distance Units:
- 1 Astronomical Unit (AU) = Earth - Sun Distance
- = 93 million miles
- = 150 million km

What is the origin of the Universe?

- The two simplest atoms (H and He) were created during the Big Bang.
- More complex atoms were created in stars.
- When the star dies, chemical elements are expelled into space…. to form new stars and planets!

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

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.

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…

The Earth orbits around the Sun once every year!

The Earth’s axis is tilted by 23.5º!

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!

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!

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!

The Milky Way moves with the expansion of the Universe!

- Mostly all galaxies appear to be moving away from us.
- The farther away they are, the faster they are moving.
- Just like raisins in a raisin cake; they all move apart from each other as the dough (space itself) expands.

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