HR Diagram Inference Lab

Stars • ASTR201 • 14 min

Context

This station is designed to be completed quickly. Write a prediction, follow the steps, then make a claim supported by evidence from the demo.

Predict

Before revealing mass colors, predict where high-mass and low-mass stars should lie along the main sequence.

Prediction (1 sentence):

Play steps

  1. Start in Observer CMD mode and identify main sequence, giant-branch, and white-dwarf structures.
  2. Switch to Theorist HR mode and enable radius lines to infer stellar size from L and T_eff.
  3. Use the evolve-a-star tool to compare track shape and timescale for 0.8 and 20 M_sun stars.
  4. Reveal mass colors and infer the hidden mass gradient direction along the main sequence.
  5. Add one-sentence claims to the inference log and export JSON.

Parameter table

Parameter Value What to notice
Mass M 1 Msun Use as a baseline before moving to higher or lower masses.
Metallicity Z 0.02 Solar-neighborhood reference for initial comparisons.

Explain

Explain how the same population can be interpreted as an observer CMD and a theorist HR map, then justify one radius and one mass inference.

Explanation (2–3 sentences):

Claim + evidence

Claim:
Evidence (what you observed):