Question

The picture shows seven stellar absorption spectra with type O at the top, B next, and so on down to M at the bottom. Only the blue part of the spectrum is shown. The strength of the line is determined by how dark the line is. In the next problem is shown a digital version of the same spectra in randomized order. The intensity is the vertical axis. In both pictures, the horizontal axis is wavelength.

1. Match the letter of the digital spectrum with the number of the photographic spectrum. (Spectrum (1) refers to the photographic spectrum labeled (1) in the first picture.)

1) spectrum (4)
2) spectrum (7)
3) spectrum (5)
4) spectrum (2)
5) spectrum (1)
6) spectrum (6)
7) spectrum (3)

2. Order the digital spectra above (shown in the second picture) from hottest to coldest. (Answer ABCDEFG, or DCBFGEA, or whatever is the correct order for your picture.)

3. Match the letter located in the digital spectra above (in the second picture) with the correct statement about each spectrum. (If the first statement corresponds to spectrum A and the rest to B, then enter ABBBBBB)

1) Lines of ionized helium; most lines are weak because the star is so hot most electrons are removed from atoms and there are few atoms making transitions.
2) Many lines of neutral elements and molecular states.
3) Lines of neutral helium. Hydrogen lines moderately strong
4) Singly ionized Calcium (393.0 nm) and a hydrogen line (434.0 nm) are about equal strength.
5) Lines of neutral elements strongest. Singly ionized calcium lines are weaker, but still present.
6) Lines of easily ionized elements like singly ionized calcium are strong; hydrogen lines are weak because it is not hot enough for hydrogen to be in the n=2 state.
7) Hydrogen lines very strong and dominate the spectrum.

4. Give the spectral type (OBAFGK or M) of the stars which produced the digital spectra shown in the second picture. If the top spectrum corresponds to K, the next to G, and the next to M etc., enter KGM...