A Day on Jupiter

Pupils will use time-staggered images of Jupiter to calculate its rotation period. In other words, they will be measuring the length of a day on Jupiter.

Resources required

Timed images of Jupiter, preferably with the Red Spot in view so that this prominent feature can be used as a reference point on the surface of the planet.

Image of Jupiter

Observation taken at 20:30 pm
Image of Jupiter

Observation taken at 00:30 am

This activity lends itself to making requests for observations of Jupiter using the Liverpool Telescope. However, the NSO data archive can be used as a source of good image data for use with this activity.

Using image processing software (LTImage) to display and measure movements on a planet's surface is highly motivational, and provides Mathematics Departments with the opportunity to include an exciting application of ICT into lessons.

Content

  1. Look at the first image of Jupiter.
  2. Select one particular point within the Great Red Spot and mark it.
  3. Find the corresponding point on the next image and mark it.
  4. Measure the distance between the two points and note this down.
  5. Measure the apparent diameter of the planet from your image.
  6. Express the distance between the positions of the Red Spot as a fraction of the diameter.
  7. This fraction is equal to the ratio of the time delay between the images to the time taken for the Red Spot to traverse the face of the planet; write these fractions as a pair of ratios, using T to denote the latter.
  8. Calculate the time taken by the Red Spot to move across the face of the planet. Multiply your answer by 2 to get the rotation period of the planet.
  9. Discuss the factors which may distort the result you obtain.
Keywords

Equivalent fractions, units, ratio, algebra, diameter

Teachers' Notes

  1. Including the Red spot in the images makes it easier for pupils to choose a suitable point to mark.
  2. Factors distorting the accuracy of the results include:
    • Marking the points of reference inccurately.
    • Measuring the distance between the points inaccurately.
    • Measuring the diameter inaccurately.

National Schools' Observatory wishes to thank
Carl Sanderson for writing this page of the Staffroom.


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