# osei_Lab4.docx - Rowan Introduction to Astronomy Lab 4 / An...

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Rowan Introduction to AstronomyLab 4 / An Introduction to Kepler’s 3 LawsName:_Stephen OseiScore:ObjectivesReproducing ellipses via the “string-and-pencil method,” students will draw ellipses and determine their eccentricities.By measuring 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.ProcedureKepler's three laws are simply a mathematical way of describing motions of objects that orbit a large central mass, such as the planetswhich 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 submittwoellipses to receive credit for this part]Kepler’s first law states thatorbiting objects travel inellipticalpaths with the central mass at one focus. In this section, you will getacquainted with ellipses by sketching one yourself.Note that the stringloopsaround the pins. DoNOTstick the pins intothe string. Make sure there is enough slack in your loop ofstring.To draw anellipseloop string around thumb tacksat each focus and stretch string tight with a pencilwhile moving the pencil around the tacks. The Sunis at onefocus.Steps to draw an ellipsecis the distance between the center oftheellipse (orbit) and one of the foci,F,which typically is the Sun or aplanet (like Earth) that is beingorbited.(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 yourstring loop around the pins. Be sure to leave some slack in the string. Use a piece of cardboard to help secure the pins ortacks.(b)Using the string as a guide (i.e., place the pencil inside the string loop and pull the loop taut), draw an ellipse.[10pts]Attach your sketch to this lab report.(c)Now measure and write down the distance between the foci andthe length of the major axis of the ellipse.[5pts]distance between foci = _25mmlength of major axis =46mm(d)Divide the distance between the foci by the length of the major axis. This quantity is known as the eccentricity, “e.”[5

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Term
Fall
Professor
NoProfessor
Tags
Kepler s laws of planetary motion, Celestial mechanics, Semi major axis