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Astronomy 104 -- Astronomy of the Solar System Spring 2009, TR 11:10-12:30, TCCW129

•  Instructor: Dr. Ting-Hui Lee •  Office: TCCW 215 •  Phone: 745-6472 •  E-mail: ting-hui.lee@wku.edu •  Office hours: W 10:00-11:45, R 2:50-3:45 or by appointment •  Course website: http://www.physics.wku.edu/~thlee/astr104/

–  Announcements –  PowerPoint slides

•  The best way to find me is by email •  Clean your INBOX!!

Required Material

•  Textbook: The Cosmic Perspective, 5th edition by Bennett et al.

Required Material

•  Mastering Astronomy http://www.masteringastronomy.com/

Course ID: LEE33249SPRING2009 First Assignment: Introduction to MasteringAstronomy

due Tuesday, Feb 3 at 11am

Registering for MasteringAstronomyTM 

www.masteringastronomy.com 

Answer the ques8on: “Do you have an access code?” 

Select:   “Yes, I have an access code” if you purchased a text with a code.   “No, I need to purchase access online now” if you do not have a code. 

Click “Con8nue” Click “Con8nue” 

Pre-Course Assessment •  http://www.wku.edu/paws/ login with your WKU ID and Topnet PIN

Do your best It’s not graded Take your time Tell the truth Before Feb. 2

Extra credit of 5pt.

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Laboratory

•  4 observing labs to be completed out of class – Constellations and Star Wheels – Motion and Phases of the Moon – Retrograde Motion of Planets – Using Sunspots to Measure the Sun’s Rotation

★ Public nights – 2nd Wednesday of every month

So what is going to happen in this course?

•  Active engagement with nearly daily group activities. – Most people required some social interaction in

order to learn effectively •  Attendance at all classes is REQUIRED. To

succeed in this course you need to be here. •  Periodic homework is REQUIRED. •  Activities outside of class are REQUIRED.

Exams

•  Test #1: Thursday, Feb. 19 •  Test #2: Thursday, Mar. 26 •  Test #3: Thursday, Apr. 23 •  Final: Monday, May 11, 8am

Grading

•  In class tests 450 pt. •  Final 240 pt. •  Labs 160 pt. •  MA assignments 150 pt. •  Total is 1000 pt. •  You need a minimum of 500 pt. to pass

Goal of the Course

Help you •  understand the physical universe •  learn how astronomy related to your daily lives •  gain skills and motivations to pursue new

knowledge using scientific method

Scientific Method is

http://www.sciencebuddies.org/mentoring/project_scientific_method.shtml

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In what ways do all humans employ scientific thinking?

•  Scientific thinking is based on everyday ideas of observation and trial-and-error experiments.

Astronomy or Astrology?

•  Astronomy – The study of the origin, evolution, motions,

compositions, and nature of celestial objects – Discipline fits the criteria of scientific method

•  Astrology – The foretelling of human disposition and future

based on the positions of the Sun, Moon and the Planets

– Discipline does not fit the criteria of scientific method

Why Study Astronomy?

•  Is Astronomy just for interest and has no practical purposes? – Agriculture in ancient civilizations – Navigation in the Renaissance – Development of theories explaining motions

(Newton’s Laws) – Development of digital cameras – Understanding radio transmission – And more…

What Do Professional Astronomers Do?

A Modern View of the Universe What is our place in the universe?

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

Star 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 

Moon (or satellite)

An object that orbits a planet.

Ganymede (orbits Jupiter) 

Ida 

Asteroid

A relatively small and rocky object that orbits a star.

Comet

A relatively small and icy object that orbits a star.

Solar (Star) System

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

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The Interstellar Medium

•  The gas and dust that fill the spaces between stars within a galaxy

•  The gas is composed mostly of hydrogen and helium

•  Star-forming clouds

Nebula

An interstellar cloud of gas and/or dust

Galaxy A great island of stars in space, all held

together by gravity and orbiting a common center

M31, The Great Galaxy          in Andromeda 

Cluster of Galaxies Universe

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

all galaxies

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How did we come to be? 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 second Sun 8 minutes Sirius 8 years Andromeda Galaxy 2.5 million years

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

M31, The Great Galaxy          in Andromeda 

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 

Light-year

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

•  At great distances, we see objects as they were

when the universe was much younger.

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How far is a light-year?

€

1 light - year = (speed of light) × (1 year)

= 300,000 kms

×

365 days1 yr

×24 hr1 day

×60 min

1 hr×

60 s1 min

How far is a light-year?

€

1 light - year = (speed of light) × (1 year)

= 300,000 kms

×

365 days1 yr

×24 hr1 day

×60 min

1 hr×

60 s1 min

= 9,460,000,000,000 km

How far is a light-year?

€

1 light - year = (speed of light) × (1 year)

= 300,000 kms

×

365 days1 yr

×24 hr1 day

×60 min

1 hr×

60 s1 min

= 9,460,000,000,000 km

= 9.46 ×1012 km

Astronomical distances and sizes are very very very large. So, astronomers use different units.

One “Astronomical Unit” (AU)

average distance between Sun and Earth

•  93,000,000 miles

•  150,000,000 km

•  1.5 × 108 km

Distance Light Travels in One Year is a “Light-year” (LY)

•  9.46 × 1012 km

•  63,000 AU or 6.3x 104 AU

Can we see the entire universe?

We can’t see a galaxy 15 billion light-years away because looking 15 billion light-years away means looking to a time before the universe existed.

Mathematical Skills

•  Powers of 10 •  Scientific Notation •  Unit Conversions •  Finding a Ratio •  Variables •  Graphs

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Powers of 10

•  Multiplication and Division

•  Powers of Powers of 10

•  Addition and Subtraction

€

102 =100, 10−2 =1

102 =1

100

€

104 ×103 =104+3 =107, 107

105 =107−5 =102

€

(102 )3 =102×3 =106

Scientific Notation

•  A number between 1 and 10 multiplied by a power of 10

€

3,042→ 3.042×103

0.00012→1.2×10−4

226×102 → (2.26×102 )×102 = 2.26×104

Unit Conversion

•  The metric system

Finding a Ratio

•  Compare two quantities

Variables

•  If (i.e., x is directly proportional to y), then if x increases by a factor of 3, y wil increase by the same facto

•  If

•  If

€

x∝ y

€

x∝ 1y

€

x∝ y2

Graphs

•  Understand simple graphs

y

x