The Spectrum Lab
Starlight arrives with lines missing, and the missing lines name both the elements present and how fast the star is moving.
Phase 0 · The phenomenon
A rainbow with gaps
Two horizontal rainbow strips running from violet on the left to red on the right, each crossed by the same set of thin black lines. In the lower strip every line sits slightly to the right — toward red — of its position in the upper strip.
Spread sunlight through a prism and you get a rainbow — but look closely and it is crossed by hundreds of thin dark lines where colours are missing. Do the same with a distant star and you see a similar pattern of gaps.
For one star the whole pattern sits exactly where it does for the Sun. For another it is the same pattern, slid a little toward the red end.
No one has ever touched a star. In this lab you will read its temperature, its ingredients and its motion from those gaps — and find out what powers it and how long it will shine.
How can the gaps in starlight reveal a star's temperature, the elements it contains, how fast it moves — and what keeps it shining?
What this lab works toward
HS-ESS1-1Model how nuclear fusion in the Sun's core releases the energy that reaches Earth as light, and how long a star like the Sun can shine.HS-ESS1-3Communicate how stars build heavier elements over their lifetimes.
Plain-English summaries. The course maps these performance expectations to this lab; the official wording is published at nextgenscience.org.
The stations
- Star ColourHow does a star's colour reveal its surface temperature?
- Line FingerprintsWhich elements are in the mystery star, and how do the dark lines prove it?
- Doppler ShiftHow does a shifted line pattern reveal how fast a star is moving toward or away from us?
- Fusion ClockHow does a star's mass set how bright it shines, how long it lives, and which elements it makes?
Each station runs the same loop: predict before you see any data, investigate the model and record runs, reveal what the measurements show, then explain the gap between your prediction and the result. A claim-evidence-reasoning checkpoint and an exit ticket close the lab.
- Stars are treated as perfect thermal (blackbody) emitters. Real stellar spectra have many more lines and are shaped by the star's atmosphere.
- Only a few of the strongest lines of six elements are drawn; the Sun's spectrum has tens of thousands.
- Doppler shifts here measure motion along our line of sight only, and the speeds are small compared with light. Distant galaxies (next lab) need the expansion of space instead.
- Luminosity and lifetime use simple power laws that fit stars from about half the Sun's mass to about fifteen times it. Smaller stars live far longer — hundreds of billions to trillions of years.