Regulus
DSS image of Regulus
Overlaid DSS image of Regulus, 60' x 60' with north at top and west to the right

Aladin viewer for the region around Regulus
Hokupa, Alpha Leonis, αLeo, 32LeoA
BD+12 2149, HD 87901, HR 3982, SAO 98967, HIP 49669, Σ5006A, WDS J10084+1158A

Type  Star
Magnitude  1.4
Right Ascension  10h 8' 22.3"  (2000)
Declination  11° 58' 2" N
Constellation  Leo
Classification  B8IVn
Observing Notes

Captain William Henry Smyth
May 1, 1837    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A standard Greenwich star, with a distant companion, in the Lion's breast. A 1, flushed white; B 8½, pale purple. This object is 11 H. VI., and the details were thus, at its first registry:
    Pos. 305°05' Dist. 168".33 Ep. 1781.84
Piazzi then entered it in the Palermo Catalogue : "Duplex. Comes praecedit;" but there can be little doubt of this comes being his No. 249 of Hora IX., as I found, by repeated trials, that the Δ RA was = 9".7. By obtaining data from a reduction of his mean apparent places, the details of Piazzi, and the results of H. and S., stand thus:
    P.        Pos. 307°00'  Dist. 178".00  Ep. 1800.00
H. and S. 307°07' 174".96 1821.21
[WDS 304° 179".2 2019]
A comparison of the measures of William Herschel, and H. and S., induced a belief, that a considerable alteration had occurred in the relative places of the two stars, in a lapse of forty years, showing a physical connection between them; but I am inclined rather to attribute the differences to proper motion and instrumental errors, than to inconstancy of angle or increase of distance. Indeed, it is a wide object for this system of measuring, and a long run upon the micrometer spring. The proper motion has been thus stated:
    P....   RA -0".28  Dec. -0".01
B.... -0".23 0".00
A.... -0".27 +0".02
[Hipparchos -0".2487 +0".0055]
This star is well known as Καρδια λεοντοs, Cor Leonis, the lion's heart. It is pointed to by Aldebaran and γ Geminorum, as well as by running a line from Orion's belt through Procyon, and carrying it nearly twice as far again to the east-north-east. The prolongation of the same line, or rather great circle, will lead to Denebola, in Leo's tail. Regulus and Denebola form the longest side of an extensive quadrilateral figure, with two other stars to the north of them; there is a still more remarkable square adjoining this, γ being a corner-stone of each. Regulus is also readily found by drawing a line southwards from γ and δ Ursae Majoris, the last stars in the square; or, with the poetaster, reversing it:
From Hydra's pass through Leo's heart, (which marks th' Ecliptic Line,)
You'll rise to where, in Ursa Great, the third and fourth stars shine.
Ptolemy calls this star Βασιλισκοζ, from an opinion of its influencing the affairs of the heavens; whence comes its Latin name Regulus, a word which appears to have been first used by Copernicus as the diminutive of rex. It is the lucida of the extensive northern constellation Leo, whose stars are well disposed and conspicuous, forming the fifth asterism in zodiacal order. The classic star-gazers viewed this as the apotheosis of the Nemaean Lion, and the emblem of heat; but Stower's celebrated manuscript Almanac of 1386, recognises in it one of Daniel's lions, and therefore "whoso es born in yat syne he schal be hardy and lytherus." Schickhard insisted that it represented the Lion of the tribe of Judah, mentioned in the Apocalypse. It was under the tutelary protection of Jove himself, whence the astrologers chattered largely about an alliance between the planet Jupiter and the constellation Leo. Macrobius—De Somnio Scipionis—says that the Lion was assigned as the Sun's house, and Cancer as the Moon's, because they were in those signs "in ipsâ geniturâ mundi nascentes." The Arabs called this "fiery trigon" Kalb-al-Asad, or lion's heart, and Meliki, or kingly; for this impression of greatness was as rife among the Oriental astronomers and their successors, as among their classic predecessors. Thus Wyllyam Salysbury, treating of the sphere, or frame of the world, in 1552, tells us, "The Lyon's herte is called of some men, the Royal1 Starre, for they that are borne under it, are thought to have a royall nativitie;" and in the Tabule Astronomice Alfonsi Regis, 1492, it is written against Regulus, "Que est super cor: et dicit. Rex." Yet after all Horace only sings of it as
    Stella vesani Leonis.
Λεων, Leo, Nemeas alumnus, Bacchi sidus, Stella regia, are also names by which the Lion has been designated; and it is visible to the gazer by the large trapezium which it displays. Even should Regulus not be personally known, this trapezium is readily found by the univer- sally-known pointers of the Great Bear; for as they serve to show Polaris to the northward, so also doth the line produced by them, prolonged southward about 45, point to the Lion. It is one of the old 48 con- stellated groups, and has been thus catalogued :
    Ptolemy   . . . 35 stars    Maraldi   . . .  60 stars
Tycho Brahd . . 40 Flamsteed . . . 95
Bayer . . . . 43 Hodell . . . . 276
Hevelius . . . 50 Bode . . . . 337
The retrograde motion, owing to the recession of the equinoctial points from a slow vibration of the EartlTs axis, occasioned by planetary attractions by which the stars appear to go in antecedentia, or backwards from west to east, contrary to the order of the signs of the zodiac affords data from which the march of those heavenly bodies, in a course parallel to the ecliptic, is easily traced. This motion was first detected and reduced to rule by Hipparchus, in discussing his own observations with those of Aristyllus and Timocharis; and the longitude of Regulus has, through successive ages, been made a datum-step, by the best astronomers of all nations. From these a few may be selected, in order to show the changes of that point, since it has been under observation :
          ASTRONOMER.          DATE.      LONGITUDE.

Timocharis . . . . . B.C. 295 . . . ♋ 27° 54'.5
Hipparchus . . . . 128 . . . 29° 50'
Ptolemy . . . . . . A.D. 136 . . . ♌ 2° 30'
Abd-r-ahman Súfi . . 964 . . . 15° 12'
Chrysococcas Persa . 1115 . . . 17° 30'
Ulugh Beigh . . . . 1437 . . . 19° 55'
Tycho Brahé . . . . 1587 . . . 24° 06'
Flamsteed . . . . . 1689 . . . 25° 31'.3
Maskelyne . . . . . 1770 . . . 26° 38'
Airy . . . . . . . 1840 . . . 27° 36'.3
The Astronomer Royal, Mr. Airy, sent me his position of this star to rigid exactness. "Our catalogue place of Regulus," he obligingly wrote, "from the observations of 1840, is as follows:
     Mean RA    1 Jan. 1840 =  9h 59m 50s.71
Mean N.P.D. = 77h 15m 12s.43
"With these, and the mean obliquity= 23° 27' 36".52, the latitude and longitude will be computed thus:
    Longitude   . . . . . 147° 36' 20".15
Ecliptic N.P.D. . . . 89° 32' 25".12"
These data afford a striking instance of the sagacity of the early astronomers. They, however, considered the equinoxes to be immovable; and ascribed the change of distance of the stars from it, to a real motion of the orb of the fixed stars, which they supposed to have a slow revolution about the poles of the ecliptic in the Platonic period of 25,920 years, a space not remotely different from that produced by moderns, from other principles. Sir Isaac Newton very ably demonstrated, that the physical cause of the precession arises from the broad or spheroidal oblate figure of the Earth; which satisfactorily proves the operation, and accounts for the effect.
― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844
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Regulus