Session Support
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Session 1: Finding Other Worlds
SESSION 5 OF 5 · SESSION SUPPORT
Finding Other Worlds
How many planets are there that could harbor life?
45 MINUTES
ON THIS PAGE
Got 10 minutes?
Teacher tips
Misconceptions
Extension tasks
Curriculum links
GOT 10 MINUTES TO PREP?
Here's all you need to walk in and teach.
01
Session Plan
The full session: what students will learn, how to run every stage and all activity instructions.
Open the plan
02
Slide deck
Everything you put on the board, in order. Speaker notes included.
Open the slides
03
Learner Journal
Five-part reflection, used in the plenary of every session.
Editable version
Print version
04 · FOR STUDENTS
ITZA pathways
The link you share with the class for the 20 minutes online.
COMING SOON
MAIN THEME
Scientists can learn about distant planets without ever seeing them directly, by using indirect evidence and careful models. But finding a planet similar to Earth does not guarantee it can support life. Scientists must weigh multiple pieces of evidence together before reaching a conclusion.
BY THE END OF THIS SESSION, LEARNERS SHOULD BE ABLE TO
Explain why finding planets around distant stars is so difficult.
Describe the wobble method and the transit method for detecting exoplanets.
Explain what the habitable zone is and why it matters for the search for life.
Describe what the Earth Similarity Index measures and why a high score does not guarantee life.
Identify gases that could be biosignatures and explain why no single gas is enough evidence on its own.
Weigh multiple pieces of evidence to make and justify a reasoned decision about a planet's habitability.
Teacher tips
These are the notes from teachers who have run the session.
Hook
Build up gradually: naked eye, then telescope, then exoplanets. Each step should feel like a step further out, that's 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 close enough to see without a telescope. Worth stating clearly if it comes up, since it's an easy thing to get backwards.
Don't correct the thumbs up / thumbs down round on the spot. 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, have the runaway greenhouse effect ready: its thick atmosphere traps heat and the surface reaches 460°C.
ITZA platform
On Pathway 1, 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, 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, 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 don't correct it early, let round 2's radiation twist do 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. Hold groups to all three, it's what stops the pitch turning into just a planet name.
The debrief question matters more than the final answer: which round changed their 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. Push learners to answer with actual evidence from today (distance, size, atmosphere) rather than a number pulled from nowhere.
Misconceptions to watch for
THEY'LL SAY
"Scientists can see exoplanets through telescopes like photos."
ACTUALLY
Almost all confirmed exoplanets have been detected indirectly, through their gravitational effect on their star or the dimming they cause as they pass in front of it, not by direct imaging. Of over 6,000 confirmed planets, only a tiny handful have ever been directly photographed, and they just look like blurry single pixels of light.
THEY'LL SAY
"A planet that looks like Earth must be able to support life."
ACTUALLY
A high Earth Similarity Index score means a planet shares some characteristics with Earth, such as size or distance from its star. It doesn't confirm liquid water, a breathable atmosphere, or life. Venus is a good example, it's almost identical to Earth in size and sits close to us, but its surface is hot enough to melt lead.
THEY'LL SAY
"Finding oxygen on a planet proves there is life there.'"
ACTUALLY
Oxygen alone isn't conclusive, it can form through non-biological processes too, like sunlight breaking apart water vapour. Finding oxygen alongside methane is a much stronger signal, because the two gases react with each other and would disappear quickly unless something kept replenishing them.
Extension tasks
INVESTIGATE
AI Breakthroughs
Breakthroughs in AI mean scientists can hunt for planets quicker than ever before. Discover how machines are helping speed up the search for other worlds.
Machines that think
REFLECT
Opening the sky
One simple invention came first: a way to make glass clear enough to see through properly. Trace the invention that opened up the sky for everyone that followed.
The invention that opened up the sky
Buit from GET SET Space
Our full 15-session programme into the science of the universe.
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