Astrophysics 07 - Stars as Black Bodies

Give the definition of a black body.

A theoretical object that absorbs and emits all wavelengths of light perfectly.

Give the curves of black bodies.

How do we use black body curves with relation to stars?

Stars behave very similarly to black bodies, so we can use black body curves to approximate the emission spectra of stars, and to estimate it’s temperature along with other properties.

Explain Wein’s Displacement Law.

The most prominent wavelength of light is related to the temperature of the star.

Give the equation for Wein’s Displacement Law.

Peak wavelength x temperature = Wein’s constant

λ_max T = 2.9 ×10^-3 Wm

Explain Stefan’s Law.

Relates the power output of a star to its size and surface temperature.

Give the equation for Stefan’s Law.

Power output = Stefan’s constant x surface area x (temperature)⁴

P = σAT⁴, where σ = 5.67 ×10^-8 W m^-2 K^-4

Give the equation for intensity in terms of power output and distance.

Intensity = power output / (4π x distance squared)

I = P / 4πd²