Skip to main content
Sandbox Physics

Optics 052 · Interference, coherence, cavities, and metrology

Stellar Interferometer

An independently initialized three-dimensional apparatus connects Single-star diameter, First visibility null, Binary-star separation. Two dimensional physical controls, direct probe dragging, a detector trace, and three quantitative checks are recalculated from the stated equation.

Interactive modelStellar Interferometer
Primary prediction P1\mathcal P_10.500.50
Physical scale P2\mathcal P_250%50\%
Limit check V\mathcal V0.00π0.00\pi
Model regimevalid model regime\text{valid model regime}

Physics tutorial

How to investigate Stellar Interferometer

BackgroundStellar Interferometer is one independently initialized apparatus with three linked investigations: Single-star diameter, First visibility null, Binary-star separation. Its two controls—Baseline and Angular diameter—feed the governing relation V(B)=2J1(πBθ/λ)πBθ/λV(B)=\frac{2J_1(\pi B\theta/\lambda)}{\pi B\theta/\lambda}. The validity indicator marks the paraxial, lossless, weak-field, or steady-state assumption used by this apparatus.

Why it mattersHow can visibility versus baseline reveal a star too small for either telescope to resolve?

Start with the essentials

Focus question
How can visibility versus baseline reveal a star too small for either telescope to resolve?
One-sentence intuition
The detector curve and all three numerical readouts are recomputed from V(B)=2J1(πBθ/λ)πBθ/λV(B)=\frac{2J_1(\pi B\theta/\lambda)}{\pi B\theta/\lambda}. Geometry and glow are presentation encodings; the equation, units, conservation or limit check, and validity indicator are the quantitative evidence.

Core mathematical model

Governing relation

V(B)=2J1(πBθ/λ)πBθ/λV(B)=\frac{2J_1(\pi B\theta/\lambda)}{\pi B\theta/\lambda}

The implementation evaluates this relation with dimensional inputs and an executable analytic or numerical benchmark. The validity indicator marks the paraxial, lossless, weak-field, or steady-state assumption used by this apparatus.

Common difficulties

Mistaking glow for measured power

Typical misconceptionA brighter cinematic trail must represent proportionally more optical power.

Better mental modelUse the detector and normalized readouts for comparison. Glow is deliberately nonlinear so weak structure stays visible.

Run the experiment

  1. 01

    Scene 1: Single-star diameter

    Select Single-star diameter. Sweep Baseline, hold Angular diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  2. 02

    Scene 2: First visibility null

    Select First visibility null. Sweep Baseline, hold Angular diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  3. 03

    Scene 3: Binary-star separation

    Select Binary-star separation. Sweep Baseline, hold Angular diameter fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.