dimanche 5 octobre 2008

Ursa Major 18

ζ, Double, possibly binary, 2.1 and 4.2, brilliant white and pale emerald.

Mirak was an early name for this, a repetition of that for β; but Scaliger incorrectly changed it to the present Mizar, from the Arabic Miʼzar, a Girdle or Waist-cloth, which, although inappropriate, has maintained its place in modern lists; Mizat and Mizra being other forms. There is evident confusion in the early use of this word as a stellar title, for it has also been applied to the stars β and ε of this constellation. The "hill Mizar" of the 42d Psalm sometimes is wrongly associated with this, the original Hebrew word miṣʽar being better rendered in the Psalter, from Coverdale's version, as "the little hill," i.e. of Hermon, of which it was a minor peak.
ζ also was the Arabic ʽAnāḳ al Banāt, the Necks of the Maidens, referring to the Mourners at the Bier; or perhaps this should be rendered "the Goat of the Mourners," for in some editions of Ulug Beg's Tables it was written Al Inak, — correctly Al ʽInz. Assemani said that it was "Alhiac," the Ostrich, probably another of his errors, as all these stellar birds were much farther south, in or near our River Eridanus.
With Alcor it has various combined titles noted at that star; and Wetzstein repeats an Arabic story in which Mizar is the wālidān of the Banāt, with Alcor as her new-born infant.
In India it may have been Vashishṭha, one of the Seven Sages.
ζ was the first star to be noticed as telescopically double, — by Riccioli at Bologna in 1650, and fifty years later much observed and very fully described by Gottfried Kirch and his scientific wife, Maria Margaretha Winckelmann: an association like that of the great observer Herschel and his sister, of the last century, and of Sir William and Lady Huggins in their spectroscopic work of to‑day. As early as 1857 it was successfully daguerreotyped, with others surrounding, by the younger Bond of the Harvard Observatory, although Wega had been pictured by the same process at the same observatory seven years previously by the elder Bond.
The components are within 14ʺ of arc of each other, with a position angle of 149°.5, and may be a binary system with a long period of revolution; while Pickering has shown, by study of its spectrum photographed in 1889, that the brightest component is itself double, the two bodies, of nearly each brightness, revolving around their common centre of gravity at a speed of 100 miles a second in 104 days, 140 millions of miles apart, and with a united mass forty times that of our sun. This spectrum is Sirian, and the star is in approach to us at the rate of 19.5 miles a second.
ζ is 4 1/2° from ε, and 7° from η; and a straight line from it to Polaris passes through the exact pole 1°14ʹ before reaching Polaris.
Mizar and Alcor are 11ʹ48ʺ apart, and, since they have nearly identical proper motion, some think that they may also be in mutual revolution, although so distant from each other. With their attendant stars they form one of the finest objects in the sky for a small telescope, being readily resolved by a terrestrial eyepiece of 40 diameters with a 2 1/4‑inch objective.
η, 1.9, brilliant white.

Alcaid, Alkaid, and Benatnasch are our present titles, from Ḳāʼid Banāt al Naʽash, the Governor of the Daughters of the Bier, i.e. the Chief of the Mourners. Some of the Arabic poets wrote that these Daughters — the stars ε, ζ, and η — were
Good for nothing people whose rising and setting do not bring rain.
Bayer included Elkeid in his list of names for the stars as well as for the constellation, and had authority for it from Kazwini; but he added for η "Benenaim, Bennenatz correctius Benetenasch," and in his text of Boötes alluded to it as Benenacx. The Alfonsine Tables of 1521 say Bennenazc; Riccioli, Benat Elnanschi, Beninax, Benenath, Benenatz; while Al Ḳāʼid often has been turned into Alchayr, Arago's Ackaïr, and others' Ackiar. In this Al Ḳāʼid we see the derivation, through the Moors, of the modern Spanish word Alcaide; and, with the same idea, Ideler translated the original as the "Stadtholder."
Assemani transcribed from the Borgian globe "Alcatel," Destroying. Al Bīrūnī gave it as Marīci, one of the Seven Rishis of India.
In China it was known as Yaou Kwang, a Revolving Light.
Boteler has an amusing reference to it in Hudibras:
p442 Cardan believ'd great states depend
Upon the tip o' th' Bear's tail's end;
That, as she whisk'd it t'wards the Sun,
Strew'd mighty empires up and down;
Which others say must needs be false,
Because your true bears have no tails.
η is 7° from ζ, and 26° from α; and with ζ forms another pair of pointers — towards Arcturus. It is noted as marking the radiant of one of the richest minor meteor streams, the Ursids of the 10th of November.
Bradley's earliest observations for parallax were made on this star and γ Draconis, but unsuccessfully, as his instruments were inadequate; yet even in our own day Pritchard's work on η for the same purpose showed a negative result, — 0ʺ.046, and equally unsatisfactory.
Alkaid's spectrum is Sirian, and the star is approaching us at the rate of 16.1 miles a second.
Sir John Herschel thought it, in 1847, the lucida of the seven stars.
θ, Double, 3.4 combined, brilliant white.

This, with τ, h, v, φ, e, and f in the Bear's throat, breast, and fore knees, which describe somewhat of a semicircle, was the Arab star-gazers' Sarīr Banāt al Naʽash, the Throne of the Mourners.
This space also has been Al Ḥauḍ, the Pond into which the Gazelles sprang for safety at the lashing of the Lion's tail; although Hyde applied this title to the stars now our Coma Berenices, and Ṭhufr al Ghizlān, the Gazelles' Tracks, to the small outlying stars near the Bear's feet. But the engraver of the Borgian globe placed them at stars in the neck.
In China θ, υ, and φ were Wan Chang, the Literary Illumination.
ι, Binary, 3.2 and 13, topaz yellow and purple, and κ, 3.5.

Smyth wrote that
this star has obtained the name of Talita, the third vertebra, the meaning of which is not quite clear. Ulug Beigh has it Al Phikra al Thalitha, perhaps for All Ḳafzah al‑thālithaḥ, the third spring, or leap, of the ghazal;
but he was not sufficiently comprehensive, for this last title was applied by the Arabs to ι and κ together; al Ūla, the First (leap), being shown by ν and ξ, and al Thānīyah, the Second (leap), by λ and μ, — not δ and μ as that generally accurate author asserted. In popular lists ι frequently is given as Talitha. Hyde strangely rendered the original words of Ulug Beg as the Vertebrae of the Greater Bear, — whence probably Smyth's statement, — or the Cavity of the Heel, which, from the star's position in the figure, is a much more likely translation.
In China these two stars were Shang Tae, the High Dignitary.
Holden says of ι that its "companion is suspected to be a planet." It is 12ʺ distant from the larger, and the orbital revolution is very slow.
λ, 3.7, and μ, 3.2, red.

These are our Tania borealis and Tania australis; and thing were the Arabs' Al Ḳafzah al thānīyah, the Second Spring (of the Gazelle), marking the Bear's left hind foot. Baily has them in his edition of Ulug Beg's Tables, from Hyde's Latin translation, as Al Phikra al thānia, — in the original Al Fiḳrah, the Vertebra; but this, more probably, is entirely wrong, as these three pairs of stars have always marked three of the Bear's feet.
In China they were Chung Tae, the Middle Dignitary.
ν, Double, 3.5 and 12, orange and cerulean blue, ξ, Binary, 3.9 and 5.5, subdued white and grayish white,

mark the right hind foot, and are the southern of the three noted pairs.
they were the Chinese Hea Tae, the Lower Dignitary.
The components of ξ are but 1ʺ apart, with a position angle of 300°.
ν, the northern one of the two stars, is Alula borealis, from Al Ḳafzah al Ūla, the First Spring.
ξ is Alula australis, the southern one in the combination, — Ulug Beg's Al Fiḳrah al Ūla. Ideler's Awla, and Burritt's Acola, are erroneous.
This, with ζ Herculis and γ Virginis, was the most prominent of the double stars discovered to be binary systems by Sir William Herschel in his investigations for stellar parallax, when (I quote from Professor Young),
to use his own expression, he "went out like Saul to seek his father's asses, and found a kingdom," — the dominion of gravitation extended to the stars, unlimited by the bounds of the solar system.
ξ was the first binary of which the orbit was computed, — by Savary in 1828, — having a period of sixty-one years, and has already made more than a complete revolution since its discovery. The components are about 2ʺ apart, with a position angle in 1898 of 162°.7.
The foregoing three pairs, about 20° apart and the members of each pair 1 1/2° or 2° apart, are beautifully grouped with others invisible to the naked eye. They were interesting to the Arabs, as they now are to us, and were collectively designated Ḳafzah al Ṭhibāʼ, the Springs of the Gazelle, each pair making one spring; the Gazelle being imagined from the unformed stars since gathered up as Leo Minor, and the springing of the animal being due to its fear of the greater Lion's tail. Ideler adopted this from Al Tizini and the Cufic globe at Dresden; while the Borgian globe shows a Gazelle and her Young in the same location. Kazwini, however, described this group as extending over the eyes, eyebrows, ears, and muzzle of the figure of our Ursa Major.
According to Williams the Chinese knew these six stars as San Tae, or Shang Tae; but Reeves limited this title to ι and κ. Their records mention a comet seen near by in 110 B.C.
ο, Double, 3.5 and 15.2.

Bayer said that "the Barbarians" called this Muscida, a word apparently coined in the Middle Ages for the muzzle of an animal, the feature of the Bear that the star marks.
The components are 7ʺ apart, at a position angle of 191°.4.
χ, 4, red,

placed on the right foot by Burritt as Al Kaphrah, is wrong, for Heis puts the letter at a star on the rear of the right hind quarter, and has no letter at Burritt's star; if entitled to a name at all, it should be Al Kafzah, as at ι and κ. Still the Standard Dictionary follows Burritt in its El Kophrah.
It was the Chinese Tae Yang Show, the Sun Governor, and Shaou We, of somewhat similar signification.
ψ, a 3 1/2‑magnitude yellow star, is Tien Tsan, according to Williams, but Reeves says Ta Tsun, Extremely Honorable.
ω, a 5th‑magnitude, with near-by stars, was Tien Laou, Heavenly Prison.
Between ψ and ω, somewhat nearer to the former, is the 7th‑magnitude Ll. 21185, one of the two or three stars that follow α Centauri in proximity to our system, and, so far as our present determinations can be trusted, 6 1/2 light years away.

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