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Teach Exoplanets & the Goldilocks Zone
with Universe Sandbox ²

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Exoplanet - A planet outside our solar system

Teacher Resources

The first observed exoplanet was discovered in 1988, as Canadian astronomers found the Gamma Cephei Ab planet. This finding was confirmed in 2003. As of February 2017, more than 3458 exoplanets have been discovered and confirmed, while there are over 23,000 potential candidates. Based on these findings it can be estimated that roughly every star has an orbiting planet and stars that resemble the Sun have an a planet similar to the Earth in a “Goldilocks Zone” fifth of the time.

More information you can also provide to the students:


Lesson Content

  • Theory: This lesson introduces your students to the concepts of exoplanets and Goldilocks zones.
  • Play: The students observe various exoplanets in the game.
  • Share & Discuss: These topics focus on exoplanets, Goldilocks zones and habitability.

Kepler Space Telescope

  • Space observatory that NASA launched to search for Earth-like planets orbiting other stars.
  • Launch on November 6, 2009.
  • Weight: 1,039 kg (2290lb).
  • Equipment: Schmidt camera.
  • Measures the brightness of 100,000 stars every 30 minutes.
  • Analyses the results and transmits the most interesting findings to Earth.
  • By January 2015, Kepler had discovered 1,013 confirmed and 3,199 possible exoplanets.

Kepler Space Telescope, artist's rendering.

Teacher Resources

Further resources:



Image Source: Kepler Space Telescope, Wikimedia Commons.

Planetary Habitability

What are ‘exoplanets’?

Show Notes

A planet outside our solar system which orbits a star.

Why are certain zones in solar systems considered ‘habitable’?

Show Notes

These zones are the kind of areas where Earth-like conditions could be met: in the case of a solar system, the zone where a planet is not too far away from the sun and not too close (i.e. the Goldilocks Zone).

What methods are used to detect exoplanets? You can look up information to answer this question.

Show Notes

About 97% of all the confirmed exoplanets have been discovered by indirect techniques of detection, mainly by radial velocity measurements and transit monitoring techniques.

What are ‘habitable’ planets like?

Show Notes

In determining the habitability potential of a body, studies focus on its bulk composition, orbital properties, atmosphere, and potential chemical interactions. Stellar characteristics of importance include mass and luminosity, stable variability, and high metallicity. Rocky, wet terrestrial-type planets and moons with the potential for Earth-like chemistry are a primary focus of astrobiological research. (source)

Goldilocks Zones

  • Liquid water is the foundation for life.
  • At a certain distance from the star it’s warm enough to melt the water.
  • Further away the water freezes and any closer it evaporates.
  • The sweet spot where the water melts but doesn’t evaporate is called the habitable zone (aka the Goldilocks Zone, where the temperature is just right).

Planetary habitability.

Teacher Resources

‘Goldilocks Zone’, habitable zone and Circumstellar habitable zone usually mean the same: a location where water is liquid and life as we know it is possible.


Image Source: Habitable Zone, NASA

The Trappist-1 Exoplanets

Trappist-1 Exoplanets.

Teacher Resources

  • In February 2017, the Kepler-telescope detected seven exoplanets orbiting the TRAPPIST-1 dwarf star
  • TRAPPIST-1 is a red dwarf (a small, old, relatively cool star) and the system itself is small (see scale in the picture above)
  • Three of the planets are in the habitable zone, where liquid water can appear
  • Distance from Earth is 40 light years

Image Source: Trappist-1 Exoplanets, NASA.


Lesson Goal

Open the TRAPPIST-1 simulation to complete the following in-game tasks.

  1. Observe the exoplanets in TRAPPIST-1: Which planet(s) would most likely be habitable?
  2. Add water to the planets. What happens to them?
  3. Add magnetic fields to the planets.
  4. Increase the mass of the star to 105 Jupiters. What happens?

How to modify planet details?

Show Notes

Universe Sandbox 2 enables experimenting on the planets. Click on the planet or the star and modify the details in the menu on the right side of the screen:
Basic: Mass, diameter, luminosity etc.
Motion: Orbit, scroll down to Orbital Elements to see the important details.
Temperature: Temperature of the planet and atmospheric details.
Materials: Composition, heavy minerals, water and hydrogen.
Actions: Saving the planet for further use. (Saved planets can be found in the \Universe Sandbox ²\Bodies directory).

Extra: Turn one of the planets to Earth by changing its parameters to Earth’s (mass, size, inclination, orbit). What happens to our planet?

How to Play

As you launch the game, you can immediately start playing with the Solar System.

Gameplay screenshot

To access other simulations at any time, press Esc. Then, select Open to load any of the simulations included in the game.

Gameplay screenshot

After you've clicked Open, click on any of the simulations to load them.

Gameplay screenshot

Share & Discuss

Share & Discuss

  • Which of the planets was best suited for life?
  • What happened to Earth at different distances from the star?
  • Why does the star emit flares when you increase its mass?
Show Notes
  • In the TRAPPIST-1 system, the highest probability for finding water is on planets d-f.
  • Planets b and c have been too close to the star and in its volatile early stages it may have swept any atmosphere or water off the planets.
  • Adding Earth to the system will alter the orbits of the planets unless Earth’s mass is altered to match the planet it replaced.
  • What happens to Earth depends on its distance from the dwarf star. The most likely scenario is that it will cool down significantly.
  • Many dwarf stars are volatile flare-types and Universe Sandbox 2 demonstrates this by emitting flares from the star. In reality, TRAPPIST-1 appears to be rather stable.

Tasks after Playing

What features does an exoplanet need to have in order to be considered habitable?

List three.

Show Notes
  • Oxygen in the atmosphere
  • Not too much radiation
  • There needs to be water