Finding Other Worlds

Teacher Tips

Hook

• It helps to build up gradually: naked eye, then telescope, then exoplanets. Each step should feel like a step further out, which is what makes the final “How do we even see something that far away?” land.
• The naked-eye planets aren’t stars. They’re planets reflecting sunlight, and they’re close enough to see without a telescope. It’s worth stating clearly if it comes up, since it’s an easy thing to get backwards.
• It helps not to correct the thumbs up/thumbs down round on the spot. You might let disagreements about Mars, Jupiter and Venus sit unresolved, then come back to them at the very end: “Has your answer changed now you understand the habitable zone and the Earth Similarity Index?”
• If someone asks why Venus is out even though it’s close to the habitable zone, it’s worth having the runaway greenhouse effect ready: its thick atmosphere traps heat, and the surface reaches 460°C.

ITZA Pathways

• On Pathway 1, you could ask learners to explain the wobble method and the transit method in one sentence each. If they can only describe one, that’s the one to go back to.
• On Pathway 2, it helps to push on why a high ESI score isn’t the same as proof of life. It’s easy to treat a high score as the answer rather than a starting point.
• “Which fact surprised you most?” works well here too if someone’s disengaged. There’s genuinely strange material on both pathways.

Classroom Activity

• This runs in three rounds, not one reveal. Round 1 is ESI scores alone, round 2 adds the star hazard twist, and round 3 adds atmosphere and biosignature evidence. Groups should be ranking and re-choosing after each round, not just once at the end.
• Most groups pick Proxima Centauri b in round 1 purely on ESI score. That’s the trap the activity is built around, so it’s worth not correcting it early. Round 2’s radiation twist does that work for you.
• The final pitch has three requirements: the ESI score, one extra piece of evidence, and a reason another planet was rejected. It helps to hold groups to all three, since that’s what stops the pitch turning into just a planet name.
• The debrief question matters more than the final answer: “Which round changed your mind the most?” That’s what gets at how scientists actually weigh evidence, rather than which planet “won”.

Plenary

• The reflective question returns to the big question directly: how many planets could harbour life. It helps to push learners to answer with actual evidence from today (distance, size, atmosphere) rather than a number pulled from nowhere.
• The lock-in is from Dr Sara Seager, an astrophysicist at MIT who studies the atmospheres of planets around other stars. She’s saying that an atmosphere out of chemical balance can give life away, which is the oxygen-and-methane idea from today. It’s short, so it works to read it just as it is, then ask “Why does she say ‘out of chemical balance’?”