Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.

Monitor the Time at which Jupiter rises

The purpose of this project is to show you how objects in the sky follow a schedule which does not follow our human 24-hour cycle. Your job is to watch for Jupiter over the course of 6-8 weeks and measure the time at which it first appears over the eastern horizon; you should see a regular trend in these times.

The experiment is pretty simple:

  1. Find a good place from which to watch Jupiter rise. It should
  2. From your chosen location, draw a picture of the view facing east. Show the local horizon, and indicate any impediments (bright streetlights, big trees, etc.). The picture should be a "closeup" of the eastern sky, showing about 10 or 20 degrees of the horizon across the full width of a piece of paper. If it helps to use binoculars when making the picture, go ahead. You will use this picture throughout the project.
  3. Use any tool you wish to predict the time at which Jupiter ought to rise over the course of the quarter. Make a table of rising times, one per week, from the beginning to the end of the quarter. Use this table to help yourself be ready in time to see Jupiter rise on any particular date.
  4. Find a good source of accurate time, and set your watch at least once a week. TV stations, radio stations, and the US Naval Observatory:

    http://tycho.usno.navy.mil/what.html
    are all fine.
  5. Now, at intervals of roughly one week, when the weather is good, go outside about 5 minutes before Jupiter is predicted to rise, and watch the eastern horizon. Note the time when Jupiter first becomes visible. It might be a small distance above the horizon when you first can see it -- that's okay. Using your picture of the horizon, mark the spot at which it first appears. It might help to use binoculars to verify that a bright spot of light is really Jupiter, and not a plane.

    Record at least 5 different rising times, marking the location at which you first notice Jupiter on your picture. Make a table of the observed and expected rising times. Answer the following questions:

    1. How well do the expected and observed rising times agree? Can you explain any big differences?
    2. Does the location at which Jupiter first appears above the horizon change over the weeks? If so, why?
    3. Why does the time at which Jupiter rises change over the course of several weeks?

    Turn in a careful description of your observing location (including your latitude and longitude, as accurately as you can), your picture, a table of observed and expected times, and answers to the above questions. You are, of course, free to hand in additional observations, notes, ideas, or other material which you collect over the quarter.

    Last modified September 7, 1999.

    Creative Commons License Copyright © Michael Richmond. This work is licensed under a Creative Commons License.