mercredi 1 octobre 2008

Cassiopeia 8

γ, Binary, 2 and 11, brilliant white,

in Cassiopeia's girdle, was the Chinese Tsih, a Whip.
This was the first star discovered to contain bright lines in its spectrum, — by Secchi in 1886 — and so is of much interest to astronomers. The spectrum is peculiarly variable, as also is its light.
The components are 2ʺ.1 apart, at a position angle of 255°.2 and there has been no change in angle or distance since measured by Burnham in 1888. A telescope of high power shows several minute companions.

δ, 3,

is Ruchbah, sometimes Rucba and Rucbar, from Al Rukbah, the Knee.
It was utilized by Picard in France, in 1669, in determining latitudes during his measure of an arc of the meridian, — the first use of the telescope for geodetic purposes.
ε, of 3.6 magnitude, nearer the foot, also has borne the title Ruchbah.
ζ, of the 4th, and η, of the 5th magnitude, marking the face, were the Chinese Foo Loo, a By-path.
η, Binary, 4 and 7.5, orange and violet,

very near α, is one of the finest objects in the sky for a moderate-sized telescope; and, although unnamed, it is worth noting that the components were 5ʺ apart in 1892, at a position angle of 193°, their period being about 200 years. The parallax is 0ʺ.15 according to Struve; or 0ʺ.45 according to Davis' measures of Rutherfurd's photographs. It is certainly a neighbor, and probably the nearest to us of all the stars in this constellation.

θ, 4.4, and μ, Triple, 5.1, 10.5, and 11, deep yellow, blue, and ruddy.

The Arabians knew these as Al Marfiḳ, the Elbow, where they lie; and the Century Cyclopedia gives Marfak as a present title for either star.
μ has the great proper motion of 3ʺ.8 annually, a rate that will carry it around the heavens in 300,000 years.

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