Final answer:
The property of a star's light that allows us to determine its temperature is its wavelength according to Wein's Law.
Step-by-step explanation:
The property of a star's light that allows us to determine its temperature according to Wein's Law is its wavelength.
Wein's Law states that the wavelength at which a star emits the most light is inversely proportional to its temperature. This means that hotter stars have shorter wavelengths of light, while cooler stars have longer wavelengths.
By studying the spectrum of a star and measuring the peak wavelength of its light, we can use Wein's Law to calculate its temperature.
Learn more about Temperature determination of stars