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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: [email protected] • 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
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