mercredi 1 octobre 2008

Cygnus 8

α, 1.4, brilliant white.

Deneb is from Al Dhanab al Dajājah, the Hen's Tail, which has become Denebadigege, Denebedigege, Deneb Adige, etc.
In the Alfonsine Tables Arided appears, and is still frequently seen for this star, as Al Ridhādh and El Rided formerly were for the constellation. Referring to this last title, Caesius termed α Os rosae, the German Rosemund, although he also designated it as Uropygium, the Pope's Nose of our Thanksgiving dinner-tables.
α also, and correctly enough, is Aridif, from Al Ridf, the Hindmost; but Bayer changed it to Arrioph, and Cary to Arion.
Bayer gave Galina as an individual title.
Mr. Royal Hill says that this and the three adjacent bright stars in the figure are known as the Triangles.
Deneb has no sensible proper motion, and hence had been considered as deserving the term, generally inappropriate, of a "fixed star"; but spectroscopic investigations made at Greenwich seemed to show motion at the rate of thirty-six miles a second toward the earth, and so only apparently stationary. Such motion, Newcomb says, would eventually carry it at some time, — probably between 100,000 and 300,000 years hence, — past our system at about 1/100 part of its present distance, making it the nearest and the brightest of the earth's neighbours. But Vogel's recent and more trustworthy measures at Potsdam give its rate as about five miles a second.
Elkin estimated its parallax in 1892 as 0ʺ.047, — practically insensible. Its spectrum is Sirian.
Photographs by Doctor Max Wolf, of Heidelberg, in June, 1891, show that it and γ are involved in one vastly extended nebula.
It rises in the latitude of New York City at sunset on the 12th of May, culminating on the 16th of September, and lies so far to the north that it is visible at some hour of every clear night throughout the year.
β, Double, — perhaps binary, 3.5 and 7, topaz yellow and sapphire blue.

Albireo, the now universal title, is in no way associated with Arabia, but apparently was first applied to the star from a misunderstanding as to the words ab ireo in the description of the constellation in 1515 Almagest. Albirco in the Standard Dictionary undoubtedly is from a type error, as also may be Abbireo, Alberio, and Albeiro, which occasionally are used.
The Arabians designated β as Al Minḣar al Dajājah, the Hen's Beak, where it is still located on our maps. Riccioli wrote this Menkar Eldigiagich; and also had Hierizim.
β is one of the show objects in the sky, and Miss Clerke, calling its colors golden and azure, says that it presents "perhaps the most lovely effect of colour in the heavens." Being 35ʺ apart, the components can readily be resolved by a field-glass. The system, if binary, has a very long period of revolution, as yet undetermined, the present position angle being 56°.
Close to β appeared a nova on the 20th of June, 1670, described by the Carthusian monk Anthelmus of Dijon. This disappeared after two years of varying brilliancy, but may still exist as a 10th- to 11th‑magnitude variable, discovered, in the supposed location, by Hind in 1852.
In the neck of the Swan, not far from β, is the variable χ2, ranging from 4.5 to 13.5 in 406 days. Sometimes, at its maximum, it is of only the 6th magnitude.
γ, 2.7, is Sadr, — incorrectly Sudr, — from Al Sadr al Dajājah, the Hen's Breast, and one of the Fawāris of the Arabs.
Reeves said that in China it was Tien Tsin, the name of a city; but this generally was given to the group of four stars, α, β, γ, and δ.
γ is in the midst of beautiful streams of small stars, itself being involved in a diffused nebulosity extending to α; while the space from it to β perhaps is richer than any of similar extent in the heavens. Espin asserts that around γ and the horns of Taurus seem to centre the stars showing spectra of the fourth type. Its own spectrum is Solar. According to observations at Potsdam, it is in motion toward us at the rate of about four miles a second.
ε, 2.6, yellow,

on the right wing, is Gienah, from the Arabic Al Janāḥ, the Wing.
Between α, γ, and this star is the Northern Coal-sack, an almost vacant space in the Milky Way; another, still more noticeable and celebrated, coincidently being located in the Southern Cross.
6° to the northeast from ε is 61 Cygni, with a parallax of 0ʺ.5, and thus, so far as we now know, the nearest star to us in the northern heavens, with the exception of La Lande 21185 Ursae Majoris. If the distance from the earth to sun be considered as one inch, that to this star would be about seven and one half miles. It also is remarkable for its great proper motion toward the star σ, — 5ʺ.16 annually, — near to which it probably will be in 15,000 years. 4000 years ago it was near ε.
It is a double 6th‑magnitude, and may be binary, the components 20ʺ apart, with a position angle of 121° in 1890. It was the first star successfully observed for parallax, — by Bessel between the years 1837 and 1840.
ζ and ρ, with two other adjacent small stars, were the Chinese Chay Foo, a Storehouse for Carts.
π , 4.8,

is Azelfafage, possibly a corrupted form of Adelfalferes, from Al Ṭhīlf al Faras, the Horse's Foot or Track; and, to quote Idler,
It follows either that the foot of Pegasus [now marked by π Pegasi] extended to this star, or that in this region was supposed to be located the feet of the Stallion which, as we shall see farther on, some Arab astronomer introduced between Pegasus and the Swan.
Or the title may be, as seems more probable, from Al ʽAzal al Dajājah, the Tail of the Hen, which it exactly marks. It is sometimes Azelfafge; but p198Bayer, with whom the word apparently first occurs, had "Azelfage id est Tarcuta." What is this last? It seems to have escaped comment by all of the authorities.
π1, with about twenty other stars in Cygnus, Andromeda, and Lacerta, was comprised in the early Chinese Tang Shay, the Dragon.
P, or Fl. 34, a 5th‑magnitude, located at the base of the Swan's neck, is one of few so‑called gaseous stars having bright lines in their spectra. It was discovered by Janson, as a nova of the 2d magnitude, on the 18th of August, 1600; was numbered 27 in Tycho's catalogue, with the designation of nova anni 1600 in pectore Cygni; and Kepler thought it worthy of a monograph in 1606. Christian Huygens, the Dutch astronomer of the 17th century, called it the Revenante of the Swan, from its extraordinary light changes; but these now seem to have ceased.

ω3, Double, 5 1/2 and 10, pale red,

is Ruchba from Al Rukbah al Dajājah, the Hen's Knee; but the three stars ω now mark the tertiaries of the left wing.
The components of ω3 are 56ʺ.3 apart, at a position angle of 86°.3; and other minute stars are in the same field.

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