Stars & the Universe — Investigation · Earth & Space Science, Grade 9
Use stellar models, diagrams, and spectra to explain energy, elements, and cosmic history.
Identify and Compare Spectral Patterns
Investigate
Can a shifted pattern still identify the same atomic fingerprint?
Plan three teaching sessions: define the model and comparison; run or analyze repeated supplied/collected records; then graph, explain, revise and submit the notebook. These independent home-study routes do not certify the school’s mandated investigations or laboratory minutes.
Materials
- Ruler
- Graph paper
- Calculator
- Supplied wavelength table
Before you begin
This is a paper-and-data investigation. Use supplied illustrative data or teacher-approved observations. Do not enter hazardous sites to collect evidence.
Plan a fair test
Compare several line wavelengths with the same laboratory reference. Treat each listed line as correctly matched; actual observations require uncertainty estimates and tests of alternative identifications.
Method
- Draw wavelength axes for the laboratory and observed spectra using the same scale.
- Mark and label all three lines for each spectrum.
- Calculate (observed − rest) / rest for each line.
- Compare the ratios and explain why several matching lines are stronger evidence than one.
- Explain what a common positive shift suggests about a distant galaxy.
- Describe evidence needed beyond one spectrum to support cosmic expansion.
Open the investigation data (illustrative)
Illustrative data created for this activity; these are not measurements from an actual site or an official reference table.
| Line | Laboratory wavelength (nm) | Observed wavelength (nm) |
|---|---|---|
| A | 400 | 440 |
| B | 500 | 550 |
| C | 600 | 660 |
Analyze and explain
- Calculate all three redshifts z.
- Do the lines move by the same number of nm or the same fraction?
- Why does this table alone not establish the universe’s age or an individual star’s temperature?
- Identify the system boundary, units and conditions held comparable.
- Explain how the graph or figure supports the mechanism rather than merely repeat its trend.
- State one uncertainty or scale limitation and design a follow-up comparison that could challenge the explanation.
What a strong explanation includes
- Shows all three redshift calculations
- Distinguishes absolute wavelength shifts from fractional change
- Links a multi-line pattern to identification
- Recognizes that broader distance/redshift evidence is needed
- Keep observations separate from model-generated or supplied illustrative records.
- Explain a revision using the evidence and a stated model limitation.
Parent / teacher guide: discuss after the investigation
Each wavelength is multiplied by 1.10, so z = 0.10 for every line. Absolute shifts differ. A consistent pattern supports the proposed identification and a common redshift. Redshift together with distances across many galaxies supports an expanding-universe model; one ideal spectrum alone does not measure the universe’s age or a star’s temperature. A complete notebook also specifies the boundary, measurement units and matched conditions. Describe a mechanism connecting the pattern to the claim, then state a limitation and an additional comparison. Supplied illustrative outcomes are not a claim about your collected results; differences must be interpreted rather than corrected to match the example.
Compare this model with the learner’s actual evidence. Different measurements can support a different conclusion; check the reasoning and limitations, not matching wording.