lecture01 - Physics 20A Introduction to Astronomy...

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Unformatted text preview: Physics 20A Introduction to Astronomy Organizational Matters Professor: Aaron Barth TA: Erik Tollerud Course web page and syllabus: http://eee.uci.edu/07f/47320/ If you have questions about course material, homework, exams, grading, or anything else, PLEASE talk to me or the TA in person, either after lecture, or during discussion section or office hours. Enrollment questions All adds, drops, section changes must be done through WebReg up to October 12 For enrollment questions, go to the physics undergrad affairs offices in 520 or 524 Rowland Hall I don't sign add/drop cards for this course: go to the physics undergrad affairs offices instead Office hours Tuesday 2:00-3:00 Wednesday 10:00-11:00 Or by appointment if you can't make it during these hours Office hours are in 4109-D Frederick Reines Hall Overview of the course Main topics covered in the course: The behavior of light The night sky The solar system The sun The structure and evolution of stars Physics 20B in the winter or spring quarter covers further topics including black holes, galaxies, and the large-scale structure and expansion of the universe. Textbook "The Cosmos: Astronomy In the New Millennium" by Pasachoff & Filippenko, 3rd edition Reading for each week is listed on the schedule on the course web page One copy is available on reserve in the science library Homework Assignments There will be 8 assignments Assignments will be handed out in class on fridays and posted on the class web page Homework is due on Friday of the following week: see the web page for the schedule of due dates First homework will be due on October 5. Your lowest homework score will be dropped from your final grade Late homework will not be accepted! Homework Assignments Turn in homework in the P20A drop box Reines Hall, 4th floor, make a left out of the elevator and go down the hall Homework drop boxes are next to the wall of mailboxes Not all questions will be graded Solutions will be posted on the class web page. Homework assignments are due by 8:30 am on fridays This is before the discussion sections start Discussion Sections It is in your best interest to attend the discussion sections! They are your best opportunity to review the class material and homework problems, and ask questions. Quizzes will be given during discussion sections: during those weeks you must attend sections. Quizzes and Exams 2 quizzes, given during discussion sections: October 19 November 30 Midterm exam November 2 Final exam December 10, 1:30-3:30 Quizzes and Exams All quizzes and exams will be multiple-choice For the quizzes and exams, you must bring a Scantron form #288 and a pencil "FORM NO. F-288-PAR-L" This is the big red form with room for 200 questions. Calculators will not be allowed. No make-up exams will be given for the quizzes, midterm, or final. Grading Policy Final grades will be based on: Homework assignments: 10% Quizzes: Midterm exam: Final exam: 20% 25% 45% Grading Policy Final grades will be determined by a curve the class median will correspond to the cutoff between a B- and C+. Note: for students taking the course P/NP, a P grade corresponds to a C or better How to do well in this class Attend lectures Read the book (before lectures is best!) Attend discussion sections and ask questions! Do the homework and go over the solutions for all the homework problems Come to office hours (mine or Erik's) with questions How to do poorly in this class Don't come to class regularly Don't read the book or study until the last minute before an exam Don't attend discussion section regularly Don't go over the homework solutions for all the questions Don't ask questions, even if you don't understand something and need help The Math We will be using math to understand many important concepts such as planetary orbits. But the math isn't intended to be difficult! You should be comfortable with: Scientific notation Multiplication and division Powers and exponents, square roots No calculators will be allowed in the exams Exams will include a list of relevant equations Lecture notes Lecture slides will be posted on the course web page as a pdf file after each lecture Reading the lecture slides is not a substitute for attending class! The UCI Observatory Next visitor night: November 2 see http://www.physics.uci.edu/~observat/ http://www.physics.uci.edu/~astroclb/ Learn to use the telescopes- join the UCI astronomy club Astronomy: The study of the structure, origin, and evolution of the cosmos The night sky, and the positions and motions of the stars and planets Understanding the physical processes that occur in celestial objects Origins: how did the universe begin? How do stars and planets form? How did life begin? Some preliminary definitions Star: A luminous, gravitationally bound ball of gas that shines because of nuclear fusion reactions occuring in its core. Planet: An object of substantial size (diameter greater than about 1000 km), but not massive enough for nuclear fusion reactions to occur in its core. Moon: An object in orbit around a planet. Solar System: The system consisting of the Sun and all of the planets, moons, asteroids, comets, and other material in orbit around it. Nebula: a cloud of gas, often associated with star-forming regions, or resulting from the death of a star Constellations: groupings of stars in the sky thought to resemble animals, monsters, or mythological characters Telescope: a device used to gather light and bring it to a focus. More definitions Galaxy: A very large collection of stars held together by gravity. Large galaxies contain hundreds of billions of stars. Our solar system is in the Milky Way galaxy. The Universe. Everything that exists: all the galaxies and their contents, and all of the space between them. We can only directly observe a small part of the Universe, and the entire Universe might actually be infinite in extent. You are here Units of Measurement Length: meter (m) 1 m = 39.37 inches 1000 g weighs 2.2 pounds (on earth) Mass: gram (g) Time: second (s) Temperature: Kelvin (K) K = Celsius (or Centigrade) temperature + 273 0 K = absolute zero Prefixes for large and small numbers (G) Giga = 1,000,000,000 = (M) Mega = 1,000,000 = 106 (k) kilo = 1000 = 103 (c) centi = 1/100 = 10-2 (m) milli = 1/1000 = 10-3 9 10 () micro = 1/1,000,000 = 10-6 (n) nano = 1/1,000,000,000 = 10-9 The Speed of Light In vacuum (empty space), light travels at a constant speed of 299,792,458 meters per second For our purposes, round off to 3108 m/sec, or use 3105 km/sec The Sun is about 150 million km away. How long does it take for light to travel from the sun to the earth? time elapsed = (distance traveled) / speed Units for Large Distances 1 Astronomical Unit = mean distance between earth and sun 1 AU = 1.4961011 m Eris, the most distant detected object in our Solar System, is currently 97 AU away from the Sun The nearest star to the sun (Proxima Centauri) is 266,000 AU away! Units for Large Distances 1 light-year = distance traveled by light in 1 year 1 LY = 9.461015 m 1 parsec (1 pc) = 3.26 LY (we'll find out why later on) Proxima Centauri, the nearest star to the Sun, is 4.2 LY away Units for small distances micron: nanometer: ngstrom: 1 m = 10-6 m 1 nm = 10-9 m 1 = 10-10 m These will be used often to describe wavelengths for optical or infrared light. Units for Large Masses Earth mass: 61024 kg Jupiter mass: 317.9 Earth's mass Solar mass: 333,000 Earth's mass 1 M = 21030 kg A large spiral galaxy can have a total mass of around 1012 M (that's 1 trillion solar masses!) Looking back in time When we observe light from distant astronomical objects, we see what those objects looked like at the time when the light was emitted! Nearest star: 4.2 LY away Center of the Milky Way Galaxy: 25,000 LY away Nearest big galaxy: 2.4 million LY away Most distant known galaxies: 13 billion LY away! Timescales Age of the universe: 13.7 billion years Age of the oldest star clusters in the Milky Way Galaxy: about 13 billion years Age of the Sun and Solar System: 4.6 billion years Earliest known life on Earth: about 3.5 billion years ago (fossilized remnants of bacterial colonies) Dinosaur extinction: 65 million years ago Homo Sapiens appeared: about 350,000 years ago UC Irvine founded: 42 years ago Timescales If we condense the entire history of the Universe into one year, the calendar would look like this: January 1: the Big Bang February: formation of the Milky Way galaxy August: formation of the Earth December 25-30: dinosaurs The entire history of human civilization would take place during the last 10 seconds of December 31! ...
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This note was uploaded on 04/20/2008 for the course PHYS 20A taught by Professor Staff during the Fall '02 term at UC Irvine.

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