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Spectroscopic Atlas for Amateur Astronomers 87

Table 52: Luminosity effects on spectra of the late K-class: Alsciaukat (α Lyncis) and
61 Cygni B.

61 Cygni B (11 ly) is the weaker of two binary components. With K7 V it’s classified as an
ordinary Dwarf on the Main Sequence. The surface temperature is some 4,120 K, its ap-
parent rotation speed is <2km/sec. The two components belong to the few true Main Se-
quence Stars of the K-class which are spectroscopically accessible to moderate sized tele-
scopes.

Alsciaukat (220 ly): This star with the jaw-breaking, Arabic name is classified with K7 lll,
and thus a Normal Giant. Its surface temperature is about 3,860 K. Its apparent rotation
speed could not be found. Its slight variability suggests that it stands just before a long-
period, Mira-type variable stage [506].

The comparison of the two equally normalised spectra shows in this section a similar pro-
file shape for the different luminosity classes. In each section, however, clear differences
and even different lines are visible. The spectrum of Alsciaukat shows at this resolution
(according to BSA) clearly the splitting of the former Fraunhofer G -band into three discrete
absorption lines: Ti l (λλ 4301 and 4314) and Fe I (λ 4308).

Table 53: Aldebaran (α Tau)

Complementary to Table 52 some higher-resolved detail spectra
of the K-star Aldebaran (66 ly) in the green and red region are
added here (900L grating). Aldebaran with K5 III represents the
later K-class and is established on the Giant Branch of the HRD.
Its surface temperature is about 4,010 K. The apparent rotation
speed is given in [505] with <17km/s. The graphic shows the
proportions of Aldebaran compared to the Sun.