The brightest star in the constellation → Draco,
with a visual magnitude of V = 2.23 and color B - V +1.52. It is a
cool (4000 K) → giant star of
spectral Type K5 III, lying 148 → light-years. Gamma Draconis has
a luminosity 600 times that of the Sun and a diameter 50 times that of the Sun.
It crosses the sky near the zenith point for England, a nd this was the reason why
James Bradley (1693-1762) observed γ Draconis
when he was trying to detect parallax and so calculate the distance.
He found that the star undergoes a yearly shift of a form quite different
from that expected from parallax. In a 1728 paper, Bradley announced
his discovery and explained the effect as due to the
→ aberration of starlight . Variant names:
Etamin, Etanin; Ettanin, other designations:
HR 6705, HD 164058.
See also: From Ar. At-Tinnin (التنین) “the great serpent,” the Ar. rendition
of the Greek constellation → Draco.
