Activity 2 - Observing retrograde motion using Stellarium

In this activity, students will use the Stellarium digital planetarium to visually explore retrograde motion of planets, observing their positions relative to stars and constellations, and taking notes on their movements. This exercise provides a modern visual aid for understanding retrograde motion and prompts students to consider how Indigenous Peoples in the past observed and recorded such phenomena in their oral traditions without the use of computers.

Step by step guide

Step 1: Familiarise with Stellarium application

See Activity card What is Stellarium? if not familiar with this application.

Step 2: Exploring retrograde motion

It is useful for students to see how retrograde motion works visually, and to provide some local examples. You can use the digital planetarium software Stellarium ⁰ to accomplish this. This can be done by the teacher at the front of class, or students in smaller groups.

Step 3: Guided exploration with students

Download and open the Stellarium program Desktop application.

Under the “Sky and Viewing Option’ Window on the left (F4 will get you there), click on Markings tab (the fourth entry along the top series of tabs). Select “Ecliptic of date”.

On the “Sky” tab (first tab along the top) in the same window, select “Show Planet Orbits”.

In the “Date/Time” window (hover over the left-hand side of the screen or press F5), move the clock forward to when it is dark. You may need to press ‘P’ to show the night sky.

Have the students note the positions of the planets with respect to background stars and constellations.

Move the date forward (but not the time), day by day, so the students can see how the planets move.

Have students take notes by seeing how far the planet is from one or two reference stars each night. Ask them to find out when the planets are moving in retrograde (‘backward’).

Step 3: Independent exploration

Allow the students to play with the program, asking if they can find a date when the planets come into conjunction with the Moon or each other.

This serves as a visual aid, enabling the students to see how careful observations are needed to note things like retrograde motion.

Step 4: Discussion

Without the use of a computer, how did Aboriginal and Torres Strait Islander Peoples in the ancient past observe and record this phenomenon in their oral traditions?