AST 103 The Solar System

Transcription

1 AST 103 The Solar System Prof. Ken Nagamine Dept. of Physics & Astronomy UNLV Pick up two items from the front table (one each): 1. Syllabus 2. ABCD card 1

2 Instructor Contact Info Prof. Ken Nagamine Office: BPB 242 Tel: Dept. of Physics & Astronomy (best way) TA: Mr. He Gao ( ) office: BPB 247 2

3 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: 3

4 Textbooks Bennett et al, Cosmic Perspective, 6th edition Prather et al, Lecture-Tutorials for Introductory Astronomy, 2nd edition - BRING THIS TO CLASS EVERY DAY 4

5 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 5

6 A look at the Syllabus This is our contract with one another! Note the Test days and the Final Exam date! 6

7 Lecture Tutorials What is it? 7

8 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 8

9 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. 9

10 Former students speak out 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. 10

11 Any Questions? 11

12 Find your partners and form study groups to do the lecture tutorials. 3 min 12

13 Overview Chapter 1 Our Place in the Universe 13

14 1.1 A Modern View of the Universe Our goals for learning: 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? 14

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16 Hierarchy of Structure ~10 21 km ~10 19 km -- our place in the Universe ~10 18 km ~10 4 km ~10 10 km 16

17 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. 17

18 Moon (or satellite) An object that orbits a planet. Ganymede (orbits Jupiter) 18

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20 Star (Sun is one of them) A large, glowing ball of gas that generates heat and light through nuclear fusion 20

21 The Solar system A star and all the material that orbits it, including its planets and moons AU AU 1 AU 1 AU(astronomical unit)= 1.5x10 8 km 21

22 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. 22

23 Quiz 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. 23

24 Asteroid A relatively small and rocky object that orbits a star. Ida 253 Mathilde, an asteroid measuring about 50 kilometers (31.1 miles) across. Photograph taken in 1997 by the NEAR Shoemaker probe. 24

25 Comet A relatively small and icy object that orbits a star. 25

26 Nebula An interstellar cloud of gas and/or dust 26

27 Galaxy A great island of stars in space, all held together by gravity and orbiting a common center M31, The Great Galaxy in Andromeda 27

28 Universe The sum total of all matter and energy; that is, everything within and between all galaxies 28

29 Now, some basic stuff. 29

30 SI units (Systeme Internationale d Unites) (International System of Units; established 1960) Length -- Meters (m) 1 mile = 1609m = km (kilo=1000) Mass -- Kilograms (kg) 1 kg = lb, 1 lb = kg Time -- Seconds (s) 30

31 Scientific Notation (Appendix C.2) Express numbers in the general form of A x 10 n which is convenient for both large and small numbers 3, x x ??? 31

32 Powers of Ten nanoa billionth n microa millionth! millia thousandth m centia hundredth c one 1, kiloa thousand K 1,000, a million mega M 1,000,000, a billion giga G 1,000,000,000, a trillion tera T 32

33 Astronomer s Units Astronomical Unit (AU) 1 AU 1.5 x 10 8 km Light year (lyr) Parsec (pc) 1 lyr = 9.5 x km Nearest star (alpha centauri) is 4.4 lyrs away. 1 pc = 3.26 lyr = x meter 33

34 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] 34

35 Quiz 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 35

36 How can we know what the universe was like in the past? Light travels at a finite speed (300,000 km/s). Destination Moon Sun Sirius 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. 36

37 Example: We see the Orion Nebula as it looked 1,500 years ago. M31, The Great Galaxy in Andromeda 37

38 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 38

39 Light-year The distance light can travel in one year. About 10 trillion km (6 trillion miles). 1 lyr = 9.5 x km Nearest star (alpha centauri) is 4.4 lyrs away. 39

40 At great distances, we see objects as they were when the universe was much younger. 40

41 Can we see the entire universe? 41

42 Quiz Why can t we see a galaxy 15 billion light-years away? (Assume universe is 14 billion years old, and our technology is perfect.) 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. 42

43 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 43

44 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 44