How We Know What Stars Are Made Of

Lab Brief #7

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

The light you see now started its trip a long time ago.

What you'll learn

Each element absorbs light at its own set of wavelengths, leaving dark lines in a star's spectrum. Matching those lines against laboratory samples tells us a star's composition without going anywhere near it.

Key words

spectrum
Light spread out by wavelength, revealing the bright or dark lines characteristic of particular elements.
absorption line
A dark gap in a spectrum at the wavelength an element has absorbed, acting as that element's fingerprint.

Make a hypothesis first

Guess: how big does that look from here vs. from there?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

diffraction grating
gas discharge tubes
power supply
coloured pencils

Get ready

⚠️ Safety first

Use a low-voltage supply only, and never look directly into a bright source.

Step 1 of 4 · Read

Think about what you just learned: say what "spectrum" and "absorption line" mean in your own words before you start.

Step 2 of 4 · Do

View a bright lamp through a diffraction grating and sketch the continuous spectrum, then view gas discharge tubes of hydrogen and helium and sketch their line spectra. Compare the line positions and explain how a star's dark lines identify the element.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

Dark lines in a star's spectrum are produced when elements:

How sure are you?😐 maybe

Question 2 of 3

Absorption lines work as a fingerprint because each element absorbs:

How sure are you?😐 maybe

Question 3 of 3

Star composition is determined by comparing its spectrum with:

How sure are you?😐 maybe

Mind = blown

🌌 If you could drive a car straight up at highway speed, you'd reach space in under an hour.

Nice work!

You got 0 of 3 right.

Next: Measuring Distance in Space All lessons

🎯

Next Smart Experiment

We'll pick an experiment that matches exactly how you're thinking right now.

✨ More to explore

🌍 Where you see this in real life: Every sunrise and every shadow is this idea in action.

🏆 Stretch challenge (try it this week): Look at the moon tonight. Notice its shape. Look again in 3 days.

👨‍👩‍👧 For the dinner table: “If you could visit any planet, which would you pick and why?”

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