Learning Objectives
- Use curated stellar data to construct an H-R diagram and infer stellar populations and cluster age.
- Make measurements or classifications with explicit uncertainty.
- Separate direct evidence from model-dependent interpretation.
Preparation
- Read OpenStax Astronomy 2e section 18.4 on the H-R diagram and the assigned stellar evolution sections.
Materials and Data
- Instructor-provided CSV of stellar temperature/color and luminosity/absolute magnitude
- Spreadsheet or plotting tool
- OpenStax H-R diagram reference
Apparatus and Setup
- Provide a CSV with columns for star ID, color or temperature, luminosity or absolute magnitude, and optional cluster membership.
- Provide plotting instructions for spreadsheet and Python users.
- Give one reference H-R diagram for comparison but require students to generate their own plot.
Procedure
- Import or open the provided stellar dataset and identify columns for temperature or color and luminosity or absolute magnitude.
- Create an H-R style plot with temperature increasing to the left if using temperature.
- Mark the main sequence, likely giants/supergiants, and possible white dwarfs.
- For a cluster dataset, identify the approximate turnoff location and compare it with a younger or older reference cluster.
- Record plotting choices, axis units, and any data cleaning or exclusions.
Measurement Record
Use this structure or an equivalent table in your lab notebook.
| star or bin | temperature/color | luminosity/magnitude | diagram region | population | evidence |
|---|---|---|---|---|---|
Analysis and Uncertainty
- Explain why the H-R diagram is physical rather than just descriptive.
- Use turnoff position to infer relative cluster age.
- Identify one selection effect or uncertainty in the dataset.
Deliverables
- H-R diagram plot
- Population labels
- Cluster-age interpretation
- Short data/provenance note
Assessment Criteria
- Correct axes and orientation
- Reasonable population identification
- Turnoff reasoning
- Data documentation
References, Software, and Data Provenance
- OpenStax Astronomy 2e, section 18.4
- OpenStax Fig. 18.14 H-R diagram
Any additional dataset, image, or software source used by an instructor should be added to ../reference-log.md with source, access date, license or usage note, and processing steps.