Final answer:
The temperature of a star can be determined by observing its dominant color and analyzing its spectrum, specifically the peak of its power curve. Hotter stars emit more blue light, while cooler stars appear red. Spectral analysis also allows the calculation of the color index, which expresses a star's temperature.
Step-by-step explanation:
We can determine the temperature of a star by observing two aspects: the star's color and its spectrum. The color of light that dominates a star's appearance can indicate its relative temperature since hot stars emit more blue light, while cooler stars emit red light due to the difference in wavelengths associated with these colors.
Moreover, through spectral analysis, astronomers can precisely measure the temperature of a star by finding the peak of the star's power curve, which corresponds to its surface temperature. For instance, our Sun, a typical star, has an average surface temperature of 5800 Kelvin.
An additional tool used by astronomers to express the temperature of stars is the color index, which is the difference in magnitudes measured at two different wavelengths. Consequently, the color a star appears and the peak wavelength of its spectrum are crucial for understanding a star's temperature, aside from providing insights into its size, composition, and other properties.