AST 103The Solar System

Pick up two items from the front table (one each):1. Syllabus

2. ABCD card

Prof. Ken NagamineDept. of Physics & Astronomy

UNLV

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Instructor Contact Info

• Prof. Ken Nagamine

• Dept. of Physics & Astronomy

• Office: BPB 242

• Tel: 895-3485

• Email: kn@physics.unlv.edu　(best way)

TA: Mr. He Gao (email: gaohe@physics.unlv.edu ) office: BPB 247

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AST 103

• Class time: Mon/Wed 10:00a-11:15am (Section 1), 11:30am-12:45pm (Section 2)

• Location: BPB 102

• Office Hours: Thu 3:00-4:15pm, my office (BPB-242)

• Class website: http://www.physics.unlv.edu/~kn/AST103-S12/

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Textbooks• Bennett et al, Cosmic Perspective, 6th edition

• Prather et al, Lecture-Tutorials for Introductory Astronomy, 2nd edition - BRING THIS TO CLASS EVERY DAY

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What should you do?

• Read the textbook before class (lecture notes will be uploaded to the class website)

• Attend lectures and participate

• Complete Lecture-Tutorials with a partner or your study group

• Ask questions if not clear; PARTICIPATE!

• Take tests and the final exam

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A look at the Syllabus

This is our contract with one another!

Note the Test days and the Final Exam date!

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Lecture Tutorials

What is it?

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Key results from cognitive science and education research

• Learning is constructive - learning requires mental effort

• Most people require some social interactions in order to learn effectively

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Former students speak out• “I liked the Tutorial, they were very helpful. I

am not a science person but feel that I learned a lot from them.

• “Why don’t all professors use tutorials during class?”

• “The student interaction and tutorials are a very effective approach to both teaching and learning. I guarantee most students will retain most of this course.”

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• “And then the tutorials? I don’t know who ever thought of that. But it’s really how classes should be taught… The tutorials break down the concepts. You start with something so simple…and then it slowly gets to more complicated.”

Former students speak out

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Any Questions?

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Find your partners and form study groups to do

the lecture tutorials.3 min

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OverviewChapter 1

Our Place in the Universe

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1.1 A Modern View of the Universe

• What is our place in the universe?• How did we come to be?• How can we know what the universe was

like in the past?• Can we see the entire universe?

Our goals for learning:

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Hierarchy of Structure

~104 km

~1010 km

~1018 km

~1019 km~1021 km

-- our place in the Universe

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Planet

A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or

gaseous in composition.

Mars Neptune

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Moon (or satellite)

An object that orbits a planet.

Ganymede (orbits Jupiter)

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A large, glowing ball of gas that generates heat and light through nuclear fusion

Star (Sun is one of them)

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The Solar system

1 AU

1 AU(astronomical unit)= 1.5x108 km

40AU0.4

0.7

1.0AU

1.5

5.2 9.5 19 30

A star and all the material that orbits it, including its planets and moons

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The ABCD card

• Fold your card so that at any time, you can display any of the four letters.

• Write your name on the back.

• BRING THIS TO CLASS EVERY DAY!!

• If you lose it, the second copy will be $1.

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The definition of one astronomical unit is

(a) any planet’s average distance from the Sun.

(b) Earth’s average distance from the Sun.

(c) any large astronomical distance.

Quiz

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Ida

Asteroid

A relatively small and rocky object that orbits a star.

253 Mathilde, an asteroid measuring about 50 kilometers (31.1 miles) across. Photograph taken in 1997 by the NEAR Shoemaker probe.

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Comet

A relatively small and icy object that orbits a star.

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Nebula

An interstellar cloud of gas and/or dust

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GalaxyA great island of stars in space, all held

together by gravity and orbiting a common center

M31, The Great Galaxy in Andromeda

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Universe

The sum total of all matter and energy; that is, everything within and between

all galaxies

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Now, some basic stuff.

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SI units (Systeme Internationale d’Unites)(International System of Units; established 1960)

• Length -- Meters (m)

• 1 mile = 1609m = 1.609 km (kilo=1000)

• Mass -- Kilograms (kg)

• 1 kg = 2.205 lb, 1 lb = 0.454 kg

• Time -- Seconds (s)

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Scientific Notation(Appendix C.2)

• Express numbers in the general form of

A x 10n

which is convenient for both large and small numbers

3,042 3.042 x 103

0.0012 1.2 x 10-3

428 ???

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Powers of Ten

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Scientific Notation

Express numbers in a general form,

A ! 10n,

which is convenient for both large and small

numbers.

?2.3 ! 102

0.000232.3 ! 10-4

23000000000000002.3 ! 1015

23002.3 ! 103

Powers of Ten

Tteraa trillion10121,000,000,000,000

Ggigaa billion1091,000,000,000

Mmegaa million1061,000,000

Kkilo-a thousand1031,000

one1001

ccenti-a hundredth10-20.01

mmilli-a thousandth10-30.001

!micro-a millionth10-60.000001

nnano-a billionth10-90.000000001

6.4 ! 106 m 6.9 ! 108 m

5.9 ! 1012 m ~ 1021 m

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Astronomer’s Units • Astronomical Unit (AU)

• Light year (lyr)

• Parsec (pc)

1 AU ≅ 1.5 x 108 km

1 lyr = 9.5 x 1012 km

1 pc = 3.26 lyr = 3.086 x 1016 meter

Nearest star (alpha centauri) is 4.4 lyrs away.

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You are deciding which computer to buy, based on how long it takes to start running your favorite computer game. Which computer starts your game program the most quickly?

a) Game starts in 1 centisecond.

b) Game starts in 1 kilosecond.

c) Game starts in 1 microsecond.

d) Game starts in 1 millisecond.

e) Game starts in 1 second. [to choose (e), show a white side]

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Which of the following correctly lists our “cosmic address” from small to large?

a) Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe

b) Earth, solar system, Local Group, Local Supercluster, Milky Way Galaxy, universe

c) Earth, Milky Way Galaxy, solar system, Local Group, Local Supercluster, universe

Quiz

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How can we know what the universe was like in the past?

• Light travels at a finite speed (300,000 km/s).

• Thus, we see objects as they were in the past:The farther away we look in distance,

the further back we look in time.

Destination Light travel time

Moon 1 secondSun 8 minutesSirius 8 yearsAndromeda Galaxy 2.5 million years

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Example:

We see the Orion Nebula as it looked 1,500 years ago.

M31, The Great Galaxy in Andromeda

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Example:This photo shows the Andromeda Galaxy as it looked about

2 1/2 million years ago. Question: When will be able to see what it looks like now?

M31, The Great Galaxy in Andromeda

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Light-year• The distance light can travel in one year.• About 10 trillion km (6 trillion miles).

1 lyr = 9.5 x 1012 km

Nearest star (alpha centauri) is 4.4 lyrs away.

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• At great distances, we see objects as they were

when the universe was much younger.

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Can we see the entire universe?

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A. Because no galaxies exist at such a great distance.B. Galaxies may exist at that distance, but their light

would be too faint for our telescopes to see.C. Because looking 15 billion light-years away means

looking to a time before the universe existed.

QuizWhy can’t we see a galaxy 15 billion light-years away?

(Assume universe is 14 billion years old, and our technology is perfect.)

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What have we learned?

• What is our physical place in the universe?– Earth is part of the Solar System, which is in the

Milky Way galaxy, which is a member of the Local Group of galaxies in the Local Supercluster

• How did we come to be?– The matter in our bodies came from the Big Bang,

which produced hydrogen and helium– All other elements were constructed from H and He

in star and then recycled into new star systems, including our solar system

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What have we learned?

• How can we know that the universe was like in the past?– When we look to great distances we are seeing

events that happened long ago because light travels at a finite speed

• Can we see the entire universe?– No, the observable portion of the universe is about

14 billion light-years in radius because the universe is about 14 billion years old

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