# Black body Radiation

If the sun at temperature 6000K emits onto an asteroid 350million km away, what is the temperature of the asteroid assuming it is a black body?

Any suggestions how to go about this please?

## Answers and Replies

SpaceTiger
Staff Emeritus
Science Advisor
Gold Member
babtridge said:
If the sun at temperature 6000K emits onto an asteroid 350million km away, what is the temperature of the asteroid assuming it is a black body?

How much energy does the asteroid receive from the sun per unit time? How hot must it be to radiate this energy away at the same rate?

HINT: You'll need the equations for flux and the luminosity of a blackbody.

Andrew Mason
Science Advisor
Homework Helper
babtridge said:
If the sun at temperature 6000K emits onto an asteroid 350million km away, what is the temperature of the asteroid assuming it is a black body?
Determine the radiation flux incident on the asteroid using the Stefan's law:

$$P = \sigma T^4$$ where P is the total power.

$$\phi = P/A = \frac{\sigma}{4\pi d^2}T^4$$

The asteroid will absorb this radiation and raise its temperature until it is emitting at the same rate as it is absorbing, at which point its temperature wlll remain constant. The question asks you to find that temperature. It is a little tricky.

AM