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10. The Spectrum of zeta Draconis

From the lines of He I, Mg II, and Si II the spectral type would be judged to be B8. The Balmer lines are very peculiar; they are weak but do not have the sharp-edged appearance associated with high luminosity. A superficial examination might indicate that the star belongs in luminosity class II at B8. A comparison with the A0 Ib star eta Leo shows, however, that the shape of the Balmer lines - in particular Hdelta and Hepsilon - is not similar to a high-luminosity star; the contours of the H lines are more nearly like those in an early B-type dwarf.

The trigonometric parallax of zeta Dra is 0".039 ± 7 (two modern determinations). The absolute magnitude is probably fainter than zero, and it is likely that the star lies somewhat below the main sequence.