9702 · 25.2
Stellar radii
How do we measure the colossal sizes of stars that are light-years away? It seems impossible, but by observing their **brightness**, **colour**, and applying fundamental physics laws, we can estimate their **luminosity**, **temperature**, and ultimately, their **radius**. This involves several crucial steps and equations. This pilot aligns with **Senpai Corner** A Level notes (2025–2027) for topic **25.2**.
Need to know
What you need to know
- Luminosity (L) is the total power a star emits (W).
- Radiant Flux (F) is the power received per unit area (W m⁻²).
- The inverse square law, F = L / (4πd²), links these quantities with distance (d).
- Standard candles are objects of known luminosity used to measure cosmic distances.
Explanation
Stellar radii
- Luminosity (L) is the total power a star emits (W).
- Radiant Flux (F) is the power received per unit area (W m⁻²).
- The inverse square law, F = L / (4πd²), links these quantities with distance (d).
- Standard candles are objects of known luminosity used to measure cosmic distances.