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Astr 2020 Problems in Stellar Astronomy

Astr 2020 Problems in Stellar Astronomy. Tuesday 4:00 – 4:55pm Sundquist Science Center B-310 Dr. Spencer Buckner www.apsu.edu/astronomy. Office: SSC B – 326 Hours: M – F 12:30 – 2:30pm or by appointment Email: buckners@apsu.edu Phone: 221-6241. Instructor: Dr. Spencer Buckner.

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Astr 2020 Problems in Stellar Astronomy

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  1. Astr 2020Problems in Stellar Astronomy • Tuesday 4:00 – 4:55pm • Sundquist Science Center B-310 • Dr. Spencer Buckner • www.apsu.edu/astronomy

  2. Office: SSC B – 326 Hours: M – F 12:30 – 2:30pm or by appointment Email: buckners@apsu.edu Phone: 221-6241 Instructor: Dr. Spencer Buckner

  3. Textbook 21st Century Astronomy: Stars and Galaxies, 4th Edition by Kay, Palen, Smith & Blumenthal If you don’t have a book there are older versions in the department library. Most of the problems are the same but check with me before using them.

  4. Grading Exams…………45% 90 – 100…A Homework…….30% 80 – 89…..B Projects………..20% 70 – 79…..C Participation…….5% 60 – 69…..D <60……….F

  5. There will be three one-hour exams during the semester. The exams will be entirely problems similar to the homework problems. A formula sheet will be given out with the exam. Tentative exam dates are • Tuesday February 18 • Tuesday April 1 • Tuesday May 6 @ 4:00pm • A scientific calculator will be required for the exams Exams

  6. Homework Homework will be assigned from the Applying the Concepts at the back of each chapter in the 21st Century Astronomy textbook. Additional problems from other sources will also be assigned to supplement the back-of-chapter questions. They will be due at the beginning of the next class meeting. First Homework set is due next week: Chapter 1 # 41, 42, 45, 49 & 53

  7. There will be two projects assigned during the semester. The first project will be due March 4. The second project will be due at the final exam period (Tuesday May 6 @ 4:00pm). In addition to a written report, you will make a short (10-15 minute) presentation on your project. A list of potential projects for the first project will be distributed next week. Projects

  8. How to work a problem • Step 1: What are you trying to solve for? • Step 2: What information are you given? • Step 3: What equation(s) do you need to solve the problem? • Step 4: Plug in the numbers and solve the problem • Step 5: Check for reasonableness

  9. Example Problem The nearest star is Promixa Centauri, part of the triple star Alpha Centauri system. It is 4.243 lightyears from Earth. If the fastest rocket ever made, the New Horizons spacecraft, could maintain its launch speed of 16.26 km/s and it was launched at this star, how long would it take to reach Promixa Centauri?

  10. Answer the first two questions • Step 1: What are you trying to solve for?Travel time from Earth to Promixa Centauri. • Step 2: What information are you given? Speed of spacecraft (16.26 km/s) and distance from Earth to Promixa Centauri( 4.243 ly)

  11. Step 3: what equation(s) do you need? Look for example problems in the chapter, in the appendix, in other textbooks or online. For this problem, the average velocity is the distance divided by the time So the time is the distance divided by the velocity

  12. Unit Conversions Distance was given in ly and velocity was in kilometers per second. Consistent units are needed throughout. Convert distances to kilometers (or velocity to ly/sec) A word about significant figures: your calculator may spew out 8 or 9 digits but most of them are meaningless. Your answer should always have the same number of digits as the least number of significant figures in the given data. You can carry more digits through the calculations but always round off at the end.

  13. Step 4: Plug in numbers and solve d = 4.013878 x 1013 km v = 16.26 km/s

  14. Step 5: check for reasonableness Is this reasonable? How do I know if is reasonable?

  15. One for you • Use numbers from Appendix 2 and 4 in the back of the textbook to answer the following questions. • The New Horizons spacecraft, fastest spacecraft ever launched, traveled the distance from the Earth to the Moon in 8.0 hours. If it maintained that speed and it was pointed in the right direction, how long would it take to reach • Pluto? • Sirius?

  16. Step 1 & 2 Step 1: What are you being asked to solve for? Travel time to Pluto and Sirius Step 2: What information are you given? Travel time from Earth to the Moon: 8.0 hours From Appendix: distance from Earth to Moon: 384,400 km distance from Sun to Pluto: 5,906.38 x 106 km distance from Earth to Sirius: 8.60 lightyears

  17. Step 3 Step 3: What equation(s) will you need to solve the problem? First, find the speed of the spacecraft and they use that speed to find the travel time to the two objects

  18. Step 4: Plug in numbersFor Pluto

  19. Step 4 for Sirius

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