Observed Spectra

The computer simulation you did in Explore 2 assumes that all the light stars emit comes from thermal radiation. In reality, stars emit light for other reasons as well (see the Types of Stars project to learn more about these reasons).

The SDSS’s spectrograph has measured spectra for about 4,000 stars. In the next Explore exercise, you will study some of these spectra to learn whether or not they really look like the simulated spectra you studied earlier.

Explore 4. Use the Plate Browser tool to look up the spectra of several stars. Select a plate from the drop-down menu, then select a “star” link to see a spectrum. Be sure you pick a spectrum of a star.

How do the spectra of stars in the SDSS compare to thermal radiation curves? What are the similarities? What are the differences? Can you see a peak wavelength for these stars?

The Other 5,996,000 Stars

In the last two exercises, you have learned how to find the temperature of a star from the peak wavelength of its spectrum. The SDSS has measured spectra for 4,000 stars. But it has also taken images of almost 6 million stars! What can astronomers learn about those other 5,996,000 stars by studying their colors? Read on to find out.