Welcome to the Blackbody Spectra interactives. These interactive figures allow you to explore the properties of the spectra emitted by blackbodies (which are a good approximation for stars).
A blackbody is an object that absorbs all light that hits it (which would make it appear 'black' if it didn't also emit light). Though stars are not perfect absorbers of light, this assumption is very close to the truth. This allows us to use a blackbody model to simulate the light given off by stars and estimate their temperature with reasonable accuracy.
The figure on the left shows the spectrum of a model star and several other known stars. It assumes the stars are perfect blackbodies and give off is a "Blackbody Spectrum" (also called a "Planck", "Thermal" or "Continuous" Spectrum). Adjust the temperature slider until you have matched the spectra of the star with that of the blackbody model and you will have an estimate for the surface temperature of the star.
The figure on the right also shows the same spectrum, highlighting the visible potion of the spectrum. It allows you to visually see at what colors the spectrum peaks as the temperature of the blackbody changes.
As you can see using Interactive Figure 1, the temperature of a blackbody (and hopefully a star) is strongly tied to the peak wavelength of light it emits. However, the "peak wavelength" is not the only color of light given off. A blackbody gives off light of many colors, what we see is a mixture of the light emitted across the entire visible spectrum. Note: This interactive was inspired by this Flash-based UNL Blackbody Curves activity.
Now examine the interactive figure below.
The following plot shows real spectra of stars. Though we model stars as blackbodies, real stellar spectra show they are not perfect blackbodies. The real spectra of stars depend on a variety of factors beyond temperature. Some of these factors include the chemical composition of the star, the temperature dependence of the chemical's interactions with light, and so on. Despite the complications, the broad shape or "continuous" part of a stellar spectrum can typically be fit with a blackbody spectrum. Use the temperature slider to estimate the temperature of the real stars and then click the 'Show Estimated Temperature' button to see how close you were. You can select a new star, and try this again.