Overview
This lecture covers the final two layers of the Sun—the chromosphere and the corona—including their temperatures, characteristics, and why higher temperature in low-density environments doesn't always translate to more heat felt.
Observing Outer Layers of the Sun
- The layers above the photosphere are hard to see because the photosphere outshines them.
- These upper layers emit less light, making them difficult to detect without specialized methods.
- An eclipse, natural or simulated, can block the photosphere to reveal the chromosphere and corona.
The Chromosphere
- The chromosphere is a thin, colorful layer above the photosphere.
- "Chromo" means color, reflecting its vibrant appearance.
- It is hotter than the photosphere, with temperatures around 25,000 K (photosphere: ~5,800 K).
- The chromosphere looks like fire due to hot jets of gas called spicules.
- Spicules are jets bursting upward from beneath the photosphere.
The Corona
- The corona is the Sun’s outermost layer, named "corona" meaning "crown" due to its jagged, crown-like shape.
- It is extremely thin and extends several times the diameter of the Sun.
- The corona changes shape and size and is not uniform.
- Temperature is extremely high at about 2 million K.
- The full reason for the corona’s high temperature is still not well understood by scientists.
Heat Transfer and Density Analogy
- Higher temperature does not always mean you will feel hotter; density matters too.
- Example: You would burn faster putting your hand in boiling water (denser) than in a hotter oven (less dense).
- The corona, though very hot, would freeze you due to its low density (not enough particle collisions to transfer heat).
Key Terms & Definitions
- Photosphere — the Sun’s visible surface, emitting the most light.
- Chromosphere — a thin, colorful layer above the photosphere, hotter but less bright.
- Spicules — jets of hot gas in the chromosphere.
- Corona — the Sun’s outermost, extremely thin and hot layer.
- Eclipse — an event where the photosphere is blocked, revealing outer layers.
Action Items / Next Steps
- Review the posted diagram of the Sun’s layers on Discord.
- Prepare for potential discussion on why the corona’s temperature is so high.