Astrophysics – Solar Photosphere The mean surface temperature of the Sun (order of magnitude at the photosphere) is approximately:

Introduction / Context:
The Sun’s photosphere radiates like an approximate blackbody with a characteristic temperature often quoted in introductory astronomy and physics. Recognizing its order of magnitude helps relate color, peak wavelength, and emitted power using basic radiation laws.

Given Data / Assumptions:

• We are asked for an approximate, order-of-magnitude surface temperature.
• Standard textbook value is around 5778 K, often rounded to 5500°C (since °C ≈ K − 273 for large values).
• Options provide descending temperatures in °C.

Concept / Approach:
A photospheric temperature of ~5778 K corresponds to ~5500°C. Lower temperatures like 4000°C or 2000°C would imply a much redder star; 1000°C would not produce the observed solar spectrum. Thus, the best approximate value from the options is 5500°C.

Step-by-Step Solution:

Verification / Alternative check:
Wien’s displacement: λ_max ≈ 2.9×10^-3 m·K / 5800 K ≈ 500 nm (green-yellow), consistent with sunlight's visible peak—supporting a ~5800 K (≈ 5500°C) photosphere.

Why Other Options Are Wrong:

• 4000°C: Too cool; typical of K-type stars with deeper orange hues.
• 2000°C and 1000°C: Far too cool for a G-type star; would shift peak to infrared dramatically.

Common Pitfalls:
Mixing Kelvin and Celsius without adjusting. For very high temperatures, subtracting 273 is a small relative change; the order remains ~5500°C for the Sun.

Final Answer:
5500°C