Student Manual PAGE 8 The highest points in the spectrum, called the continuum, are the overall light from the incandescent surface of the star, while the dips are absorption lines produced by atoms and ions further out in the photosphere of the star. You  can measure both the wavelength  and the intensity of any point in the spectrum by pointing the cursor at it and clicking the left mouse button.  The cursor changes from an arrow to a cross, making it easier to center the cursor on the point desired. a.  Choose any point on the continuum of HD 124320 and record its wavelength and intensity below. Wavelength _____________________ Intensity ____________________ b.  Measure the wavelength and intensity of the deepest point of the deepest absorption line in the spectrum of HD 124320. Wavelength _____________________ Intensity ____________________ Note that the spectrum you see here, which is typical of those used for spectral classification, does not cover the entire range of visible wavelengths, but only a limited portion. c.  Question:  If you were to look at this range of wavelengths with your eyes, what color would they appear? ___________________________________________________ Figure 2 The Classification Window 3.  Now you want to find the spectral type of HD 124320 by comparing its spectrum with spectra of known type. Call up the comparison star atlas by dragging the LOAD pull down menu to the Atlas of Standard Spectra option.  A window will open up on which you will see numerous choices, but the atlas you want is the one at the top of the list, Main Sequence.  Select it and click on OK to load the atlas. 4.  The 13 spectra in the Atlas will come up in a separate window (see FIGURE 3), but only 4 can be seen at one time. You can look at the entire set by dragging up and down on the scrollbar at the right of the Atlas window.  Do this, and note that a sequence of representative types, spanning the range from the hottest  to the coolest are shown. List the different spectral types that are included in the Atlas on the line below, including both the letter of the class and the number of the decimal tenth of a class (e.g. G2, ...).  You can ignore the Roman numeral “V” at the end of the spectral type—this just indicates that the standard stars are main sequence stars.