lundi 29 septembre 2008

Leo 16

γ, Double and perhaps binary, 2.2 and 3.5, bright orange and greenish yellow.

Smyth wrote of this that it has been improperly called Algieba, from Al jeb‑bah, the forehead; for no representation of the Lion, which I have examined, will justify that position,—
a well-founded criticism, although as, after Regulus, it is the brightest member of the manzil Al Jabbah, it may have taken the latter's title. The star, however, is on the Lion's mane, the Latin word for which, Juba, distinctly appeared for γ with Bayer, Riccioli, and Flamsteed. Hence it is not at all unlikely that Algieba, — also written Algeiba, — is from the Latin, Arabicized either by error in transcription or by design.
Sir William Herschel discovered its duplicity in 1782, and Kitchiner asserted that this and α Lyrae are only stars upon which he ventured to use his high telescopic power of 6450. In 1784 he saw both components of γ white, and in 1803 he announced their binary (?) character. They now are 3ʺ.7 apart, at a position angle of 114°; and according to Doberck have a period of revolution of about 402.62 years, although this is very uncertain, for "since the first reliable measures of distance the change to this time is only 12°."
γ is in approach toward us at the rate of about twenty-four miles a second, the greatest velocity toward our system of any star noted by the Potsdam observers, yet only half that of ζ Herculis as determined at Poulkowa. Its spectrum is Solar.
δ, Coarsely triple, 2.7, 13, and 9, pale yellow, blue, and violet.

Zosma and Zozma are from ζῶσμα, an occasional form of ζῶμα, the Girdle, found in the Persian Tables; but it propriety as a stellar title is doubtful, for the star is on the Lion's rump, near the tail.
Ulug Beg very correctly termed it Al Ṭhahr al Asad, the Lion's Back, which has become Duhr and Dhur of modern catalogues.
With θ, on the hind quarter, it constituted the 9th manzil, Al Zubrah, the Mane, and itself bears this name as Zubra, — strange titles for star and station so far away from that feature of the animal. δ and θ also were Al Kāhil al Asad, the Space between the Shoulders of the Lion; and Al Ḣarātān, sometimes transcribed Chortan, and translated the Two Little Ribs, or the two Khurt, or Holes, penetrating into the interior of the Lion; but all these seem as inapplicable as are the other titles.
In India they marked the corresponding nakshatra, Pūrva Phalgunī, δ being the junction star between the two Phalgunī asterisms.
On the Euphrates they were Kakkab Kua, the constellation of the god Kua, the Oracle; and in Egypt, according to Hewitt, Mes‑su, the Heart of Su. In Sogdiana they were Wadha, the Wise; in Khorasmia, Armagh, the Great; and with the Copts Pikhōrion, the Shoulder.
In China δ was Shang Seang, the Higher Minister of State.
Its spectrum is Sirian, and the star is approaching our system at the rate of about nine miles a second.
Flamsteed observed it and 6 Virginis on the 13th of December, 1690, with the object which nearly a century later proved to be the planet Uranus. He made record of the observation, but without any thought of having seen a hitherto unknown member of our system.
ε, 3.3, yellow.

The Arabians designated this as Al Rās al Asad al Janūbiyyah, the Southern Star in the Lion's Head; but by us it is practically unnamed, although the Century Cyclopedia says "rather rarely Algenubi." With μ, it was Al Ashfār, the Eyebrows, near to which they lie.
It marked the 14th ecliptic constellation of Babylonia, Rishu A., the Head of the Lion.
The Chinese knew these two stars as Tsze Fe; while ε, individually, was Ta Tsze, the Crown Prince.
ζ, Double, 3.7 and 6,

Is Burritt's Adhafera, Aldhafara, and Aldhafera, by some confusion perhaps with Al Ashfār of the near-by ε and μ. It is on the crest of the mane, and was one of the manzil Al Jabhah; sometimes taking the latter's name, as in Baily's edition of Ulug Beg.
From a point a little to the west of ζ, and not much farther from γ,3 issue the Leonids, the meteor stream of November 9th to 17th, its maximum now occurring on the 13th-14th, which about every thirty-three years has furnished such wonderful displays, the last in 1866 and the next due in 1899.
Their first noticed appearance may have been in the year 137, since which date the stream has completed fifty-two revolutions. According to Theophanes of Byzantium, the shower was seen from there in November, 472; but the late Professor Newton, our deservedly great authority on the whole subject of meteors, commenced his list of the Leonids with their appearance on the 13th of October, 902, the Arabian Year of the Stars, during the night of the death of King Ibrahim ben Ahmad, and added:
It will be seen that all these showers are at intervals of a third of a century, that they are at a fixed day of the year, and that the day has moved steadily and uniformly along the calendar at the rate of about a month in a thousand years.
Oppolzer's and Leverrier's observations showed the identity of their orbit with that of Tempel's comet, I of 1866; and they are supposed to have entered our system by some comparatively recent action, as they still come in shoals and are not lengthened out in a continuous line. It was suggested by Leverrier, and confirmed by Adams, that Uranus may have produced this effect early in the year 126 of our era.
Apparently the most remarkable showers in the long Leonid history were the one observed by Von Humboldt and his companion Bonpland on the 12th of November, 1799, from Venezuela, and by various other observers throughout the western hemisphere; and that of November 13, 1833, splendidly seen from this country. The lesser one of the 13th-14th of November, 1866, was more especially noticeable from the Old World, and others, remarkable yet gradually declining, were annually seen from 1867 to 1869.
These meteors appear at an elevation of from sixty-one to ninety-six miles, during the latter part of the night, at a speed of forty-four miles a second, and generally are characterized by a greenish, or bluish, tint, with vivid and persistent trains. It probably was to them that Milton alluded in his
Swift as a shooting star
In Autumn thwarts the night.
The stream seems to be lengthening, and consequently thinning out, so that the great displays of long period may eventually cease, while the annual may become more brilliant than now.
Many other meteor streams are visible about the same time as the Leonids, Mr. W. F. Denning having given a list of sixty-eight; the brightest of these, the Ursids, being often mistaken by the casual observer for the Leonids, as their radiant, near μ Ursae Majoris, is less than 20° distant from the radiant in Leo.

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