Astr 2010Problems in

Planetary Astronomy•Wednesday 4:00 – 4:55pm

•Sundquist Science Center E-109

•Dr. Spencer Buckner

•www.apsu.edu/astronomy

InstructorDr. Spencer Buckner

Office: SSC B – 326 (enter through B-332)

Hours: MWF 10:15 – 11:30am and MWThF 1:30 – 2:30pm

or by appointment

Email: buckners@apsu.edu

Phone: 221-6241

Textbook21st Century Astronomy: The Solar System, 4th Edition, by Kay, Palen, Smith and Blumenthal

If you don’t have the book, don’t go buy it since it isn’t required. Mostly we will just use the problems in the back of the chapters. There are old editions in the department library you can borrow.

GradingExams…………45% 90 – 100…AHomework…….30% 80 – 89…..BProjects………..20% 70 – 79…..CParticipation…….5% 60 – 69…..D

<60……….F

ExamsThere 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

• Wednesday September 23• Wednesday October 28• Wednesday December 9

A scientific calculator will be required for the exams

HomeworkHomework will be assigned from the Student Questions 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 #46 & 50 plus Supplemental Problems

Solutions to the homework will be posted in the class D2L shell a day or two after they are turned in.

Project

There will be two projects assigned during the semester. The first project will be due September 30. The second project will be due at the final exam period Wednesday December 9. In addition to a written report, you will make a short (10-15 minute) oral presentation on your project.

First Project• First Project List is posted in

Problems in Planetary Astro Stuff on www.apsu.edu/astronomy and in the Content section of the class D2L website.

• NO REPEATS!

• First project presentations will be Wednesday October 21

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

Example Problem

Most objects viewed through a telescope have diameters measured in arcseconds. To calculate the linear diameter of such an object we can use the Small Angle Approximation applied to the formula for arclength (s = rq). The result is the formula where the number 206,265 comes from dividing 360° in arcseconds by 2p. If Jupiter is observed to be 31.2 arcseconds wide when it is at a distance of 944 million kilometers, what is the actual diameter of the planet?

206,265

rS

Answer the first two questions

•Step 1: What are you trying to solve for?What is the diameter of the planetJupiter in kilometers?

•Step 2: What information are you given?Angular size of the planet (31.2”)and distance from Earth to Jupiter

( 944 million kilometers)

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, it is given in the statement of the problem

206,265

rs

Step 4: Plug in numbers and solve

r = 944 x106 km

q = 31.2”

6944 10 31.2"142,791 143,000

206,265 206,265

kmrs km km

Significant figures: the final answer should never have more significant figures that the least number of significant figures in the numbers you start with.

Step 5: check for reasonableness

In this case we can check the result with the value in the back of the textbook which gives the radius as 71,492 km

An Example for YouUnder excellent seeing conditions a good sized telescope on Earth can resolve angular details as small as 1 arcsecond. What is the greatest distance at which you could resolve a typical person (1.7 meters)?

Example for You Solution1. What are you trying to find?

Distance at which 1.7 meters subtends an

angle of 1”2. What information is given?

Angle: 1”Linear size: 1.7 m

3. What equation is needed?

206,265

rs

First rearrange the equation

206,265

206,265

r ss r

Next, plug and chug

206,265 206,265 1.7350,650 350

1"

s mr km