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# Classifying Stars

Pretend for a moment that you are an astronomer living in the early 20th century, before the OBAFGKM star classification system was developed. You are one of the first astronomers who ever looked at spectra of stars, and it is up to you to develop a classification system.

The table below shows a list of the first stars you are trying to classify. Look at their spectra and divide them into several groups. There is no set number of groups you should try to achieve, and the groups do not have to have equal numbers of stars (because not all types of stars are equally common). If you find a spectrum that has nothing in common with any of the others, a group of one is OK (but on the other hand, 16 groups of one is probably not useful either!)

The table below shows a list of the first stars you are trying to classify. Spectra in the SDSS are sorted by Plate and Fiber number. Click the fiber numbers below to go to the Object Explorer entry for each star. When you click the first number, the tool will open in a new window; when you click another number, the entry for the new star will appear in the same Object Explorer window.

Once you have a star loaded into the Object Explorer, scroll down in the left-hand frame and click "Spectrum." You will see a full-sized picture of the star's spectrum. If you click "Print Page," you can print out the spectrum (but be warned that it will take a lot of ink!).

 Plate Fiber Plate Fiber 266/51630 21 266/51630 173 266/51630 275 266/51630 314 266/51630 365 266/51630 513 273/51597 2 273/51597 140 273/51597 157 273/51597 245 273/51597 589 281/51614 3 281/51614 4 281/51614 133

Exercise 1. Make a table as shown below.  Each star should fit in one of your groups.  Make notes detailed enough that another group can duplicate your work. (You may have more than four groups or fewer than four groups...this is just a sample chart!)

 Group Star(s) Characteristics