Lab 4 for astronomy.pdf - Rowan Introduction to Astronomy...

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Rowan Introduction to Astronomy Lab 4 / An Introduction to Kepler’s 3 Laws Name: ________________________________________________ Score: __________________________ Objectives Reproducing ellipses via the “string -and- pencil method,” stu dents will draw ellipses and determine their eccentricities. By measurin g the orbits of five of Jupiter’ s moons, students will test Keple’ s third law. By using characteristics of Pluto s orbit, students will confirm Kepler’ s second law. Procedure Kepler's three laws are simply a mathematical way of describing motions of objects that orbit a large central mass, such as the planets which orbit around the Sun or the moons which orbit around Jupiter. This lab explores each of Kepler's three laws. Kepler's First Law [45 pts; you must draw and submit two ellipses to receive credit for this part] Kepler’s first law states that o rbiting objects travel in elliptical paths with the central mass at one focus. In this section, you will get acquainted with ellipses by sketching one yourself. Steps to draw an ellipse (a) Get two tacks or push pins and a piece of string. On your paper, place the two tacks or pins a small distance apart. Place your string loop around the pins. Be sure to leave some slack in the string. Use a piece of cardboard to help secure the pins or tacks. (b) Using the string as a guide (i.e., place the pencil inside the string loop and pull the loop taut), draw an ellipse. [10 pts] Attach your sketch to this lab report. [Answers for (c) and (d) MUST come from your drawing; guesses are NOT acceptable.] (c) Now measure and write down the distance between the foci and the length of the major axis of the ellipse. [5 pts]
(d) Divide the distan ce between the foci by the length of the major axis. This quantity is known as the eccentricity, “e.” [5 pts] ]

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