LAB: EXPLORING ORBITS Answer Sheet



EXPLORING ORBITS :Answer Sheet

INTRODUCTION – Draw the elliptical orbit

model with Ms. Williams

SCIENTIFIC METHOD

1. Problem: What do the elliptical orbits of the planets look like?

2. Research: German astronomer Johannes Kepler solved a major puzzle of the solar system! The strange back-and forth motions of the planets in the sky were impossible to predict until Kepler figured out the true shapes of the planetary orbits around the sun. Orbits were always believed to be circular, but Kepler used mathematics to discover they were actually elliptical. An ellipse is an oval that is characterized by two quantities. The first quantity is the width of the ellipse, which is called the major axis. The second quantity is called the eccentricity, which is a measure of how stretched out the ellipse is. Eccentricity is defined by the distance between two determined points within the ellipse called the foci. This distance is between the foci is the focal length. Once Kepler understood the proper nature of orbits, the movements of the planets in the sky could be predicted with precision.

3. Hypothesis: whether the shapes of the planet’s orbits will be more circular or more elongated. ____________________________________________________________________________

4. Experiment:Data Table 1:

Formula for eccentricity= ___________________

|Ellipse (color) |Major Axis (cm) |Focal Length (cm) |Eccentricity |

| | |(distance between Sun Pin and 2nd pin) | |

|Green Planet | |10cm | |

|Red Planet | |8cm | |

|Blue Planet | |6cm | |

|Orange Planet | |4cm | |

|Yellow Planet | |2cm | |

5. ANALYSIS & 6. CONCLUSIONS

1. Look at your drawings and data table 1, then examine the pattern between eccentricity and “flatness” of your ellipses. What would the eccentricity be for a perfect circle?

|Mercury |E= 0.206 |Jupiter |E=0.048 |

|Venus |E=0.007 |Saturn |E=0.056 |

|Earth |E=0.017 |Halley’s Comet |E=0.967 |

|Moon |E=0.055 |Mars |E=0.093 |

Data Table 2:

2. Which planets have a nearly circular orbit?

3. Which planet has the most elliptical orbit?

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Here are approximate

orbital eccentricities of

some solar system objects:

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