AY2 Introduction to Astronomy Winter quarter, 2013

Transcription

1 AY2 Introduction to Astronomy Winter quarter, 2013 Instructor: Maria Fernanda (Feña) Duran Teaching assistants: Jieun Choi Katie Hamren Course web page: All the information will be there throughout the quarter

2 Course Material Textbook: The Cosmic perspective 6th edition Online homework: Course web page: All the information will be there, updated during the quarter

3 Lectures There is a lot to cover Read the chapters ahead of time Lectures will focus on clarifying and demonstrating concepts We will usually have quizzes/surveys, not graded, just for feedback. Combination of slides and some blackboard notes

4 Grading Midterm: 30% Multiple choice Final Exam: 30% Multiple choice, cumulative. Homework: 20% Discussion Section attendance: 10% In-class quizzes/surveys: 10%

5 Homework Online at Mastering Astronomy (MA), you need to buy access: Class code: AY2DURAN2013 Posted on Thursday after class. Due: following Thursday right before class. Solutions are given as you answer, allowing for instant feedback. I will post scanned solutions for quantitative problems, a few days later, so you can compare your answers step by step. One homework per week, HW0 and HW1 due next week. Extra time to get MA access.

6 Discussion sections Homework related concepts and examples will be discussed in section. Make sure you sign in every time to get credit for attendance. Come prepared! Use your time wisely and have questions ready. Give feedback to your TAs, this will make sections more useful for both you and your TA. If you need more help, come to Office Hours, ask! we can t help you unless you say something.

7 What is this class NOT about? This class is not about learning the name of the constellations Although we will talk about some history of astronomy, this is not a history class. This is a physics class

8 This is a physics class Don t panic, this is a cool physics class We will study physical concepts that will allow us to understand the universe Only high school level arithmetic and algebra. No college level math is required to pass this class. If you feel that math is not your friend, come to office hours regularly for help.

9 Math and Units Metric System Length: meters 1m = 100cm = 1000 mm 1000m = 1km Scientific Notation 1000 = =10-3 Distance to the Sun = 150,000,000,000m = 1.5 x m Wavelength of visible light = 500 nm = 5 x 10-7 m We (and your calculator) need scientific notation! Look at appendix C in Cosmic Perspective

10 Course Outline Part I: Motion of the Earth, Moon, Sun and Planets Making sense of what we can see in the night sky. Gravity: Explaining and predicting motion. Part II: Light and Energy Nature of light, light as energy Interpreting light Part III: Stars from birth to death Part IV: Galaxies and the Universe Our galaxy: the Milky way Galaxies, Quasars, Black Holes, Relativity Cosmology, the Big Bang

11 Take a few moments and fill out survey #1

12 Chapter 1: The Big picture Size and Time Scales of the Universe Physical scale: What does the solar system look like? How far away are the stars? How big is our Milky Way? How does it compare to other galaxies? How far away are galaxies? Time scale: How much time do we live? how much time do stars live? how old is the universe?

13 When we look at the stars, we are looking back in time Light travels at a finite speed c= m/s It takes 1/7 of a second to go around the Earth It takes 8 minutes for light to reach us from the Sun This means we are seeing the Sun as it was 8 minutes ago Distance to the nearest star: 3.9x10 16 m How long does light take to get to us from that star?

14 When we look at the stars, we are looking back in time Distance to the nearest star: 3.9x10 16 m How long does light take to get to us from that star? Speed of light is c= m/s or about 3x10 8 m/s speed = distance/time or time=distance/speed time= (3.9 x m) / (3 x 10 8 m/s) =1.3 x 10 8 s turning seconds into years: time = (1.3x10 8 s)x(1min/60s)x(1hour/60min)x(1day/24hour)x(1year/365days) time it takes for light to reach us = 4.11 years When we look at Alpha Centauri we are looking 4 years into the past!

15 When we look at the stars, we are looking back in time A light year a unit of DISTANCE (not time) 1 light-year is the distance light can travel in one year How much is it in meters?

16 When we look at the stars, we are looking back in time A light year a unit of DISTANCE (not time) 1 light-year is the distance light can travel in one year How much is it in meters? distance = speed x time = 3 x10 8 m/s x 1 year 1 year (in seconds)=365 days x 24 hours/day x 60 min/1 hour x 60 s/1 min 1 year = 3.1 x 10 7 s distance = speed x time = 3 x10 8 m/s x 3.1 x 10 7 s = 9.3x10 15 m

17 Some definitions

18 Comet Small icy object that orbits a star Image: Comet Garradd and M92 Broad dust tail + iron tale Credit: APOD.

19 Asteroid Small, rocky object that orbits a star Too small (too little mass) to become spherical under its own gravity In the picture: asteroid Vesta as photographed by the Dawn spacecraft. Vesta is 500 km across and is located in the asteroid belt. Credit: APOD.

20 Moon Small body object that orbits a planet Our Moon Size : 1738 km Mass: 7.3 x kg In the picture: Saturn and 6 of its moons Credit: APOD.

21 Planet Moderately massive object that orbits a star Shines by reflecting light from the star it orbits May be rocky, icy or gaseous Sizes for the solar system : x10 4 km Mass range for the solar system : kg

22 Star Massive ball of gas, mostly Hydrogen Generates light and heat via nuclear fusion Nuclear fusion happens because its own gravity produces extremely high pressure and temperature in the core. Size range : 10 1 km km Mass range : kg Our Sun: 10 6 km kg

23 Solar (star) system Collection of all the objects listed above: Sun (or a star), planets, moons, comets, asteroids.

24 Open clusters Few thousands of stars, few light-years across In the image: the Pleiades Credit: APOD.

25 Globular clusters Tens of thousands of stars, all gravitationally bound to each one another Globular clusters as the one in the picture, are about 1017 km across. They are the oldest components of our Galaxy. Credit: APOD.

26 Nebulae An interstellar cloud of gas and dust, illuminated by stars (sometimes dying or forming stars) Credit: APOD.

27 Galaxies Many billions of stars all held together by gravity. Stars live in galaxies, not scattered throughout space. Credit: APOD.

28 Clusters of Galaxies Credit: APOD.

29 Universe The sum total of ALL matter and ENERGY EVERYTHING in and between the galaxies Credit: APOD.

30 Physical Scales See interactive animation at Credit: APOD.