Exoplanets in the habitable zone
Practical Activity for 11-14
Students investigate how temperature changes with distance from a heat source and relate this to planetary temperatures.
Apparatus and materials
(per group of 2 to 4 students)
- Radiant Heater or 250 W infrared bulb mounted in a holder
- 2 thermometers (one with a shiny bulb, the other with a blackened bulb)
- 2 clamps and stands
- Meter rule
- Graph paper
Each student will require a photocopy of the instructions and worksheet.
Health & safety and technical notes
Old mains powered radiant heaters with bowl-fi re elements are no longer recommended for use in schools. Refer to CLEAPSS Laboratory Handbook 11.9.2 for safety information and alternatives. A 240 W infrared bulb works well.
Beware of burns: tell students to stop as soon as they feel anything. If a lamp is used, warn students not to look directly into the light as it will be very bright.
The practical activity
- Students use thermometers to measure the temperature at different distances from a radiant heater. They should start at a good distance (around 70 cm) from the heater and move towards it.
- Students will probably realise that the temperature will rise as they approach the heater.
- The shiny bulb thermometer should show lower temperatures as it refl ects radiation away. The blackened thermometer will absorb radiation better.
- After the students have drawn their graphs, discuss their results and explain why temperature decreases with distance from the star/heater.
- Also ask students how they think the graph would change for a more powerful heater/star.
Download the resources
The resource below includes teacher notes, a student worksheet and instructions.