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, 5 th 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 1
Registering for MasteringAstronomy TM 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 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. 2
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 2 nd 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 3
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 4
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 5
What Do Professional Astronomers Do? A Modern View of the Universe What is our place in the universe? 6
Star A large, glowing ball of gas that generates heat and light through nuclear fusion Planet Mars Neptune A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition. Moon (or satellite) An object that orbits a planet. Ganymede (orbits Jupiter) 7
Asteroid A relatively small and rocky object that orbits a star. Ida Comet A relatively small and icy object that orbits a star. A star and all the material that orbits it, including its planets and moons Solar (Star) System 8
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 9
Cluster of Galaxies Universe The sum total of all matter and energy; that is, everything within and between all galaxies 10
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). Moon Sun Sirius Destination Andromeda Galaxy Light travel time 1 second 8 minutes 8 years 2.5 million years Thus, we see objects as they were in the past: The farther away we look in distance, the further back we look in time. Example: We see the Orion Nebula as it looked 1,500 years ago. M31, The Great Galaxy in Andromeda 11
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. 12
How far is a light-year? 1light - year = (speed of light) (1 year) = 300,000 km 365 days 24 hr 60 min 60 s s 1 yr 1 day 1 hr 1 min How far is a light-year? 1light - year = (speed of light) (1 year) = 300,000 km 365 days 24 hr 60 min 60 s s 1 yr 1 day 1 hr 1 min = 9,460,000,000,000 km How far is a light-year? 1light - year = (speed of light) (1 year) = 300,000 km 365 days 24 hr 60 min 60 s s 1 yr 1 day 1 hr 1 min = 9,460,000,000,000 km = 9.46 10 12 km 13
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 10 8 km Distance Light Travels in One Year is a Light-year (LY) 9.46 10 12 km 63,000 AU or 6.3x 10 4 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. Powers of 10 Scientific Notation Unit Conversions Finding a Ratio Variables Graphs Mathematical Skills 14
Powers of 10 10 2 =100, 10 2 = 1 10 2 = 1 100 Multiplication and Division 10 4 10 3 =10 4+3 =10 7 10 7, 10 5 =107 5 =10 2 Powers of Powers of 10 (10 2 ) 3 =10 2 3 =10 6 Addition and Subtraction Scientific Notation A number between 1 and 10 multiplied by a power of 10 3,042 3.042 10 3 0.00012 1.2 10 4 226 10 2 (2.26 10 2 ) 10 2 = 2.26 10 4 The metric system Unit Conversion 15
Finding a Ratio Compare two quantities Variables If x y (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 1 y x y 2 Graphs Understand simple graphs y x 16