DSS image of Trapezium
Overlaid DSS image of Trapezium, 30' x 30' with north at top and west to the right

Aladin viewer for the region around Trapezium
Theta1 Orionis, θ1 Orionis
Σ 748, BD-05 1315, C 0532-054, WDS J05353-0523

Type  Open Cluster
Magnitude  4
Size  1'
Right Ascension  5h 35' 16.5"  (2000)
Declination  5° 23' 14" S
Constellation  Orion
Description  Association in Ori Neb θ1OriA/B/C/D/E
Observing Notes

Andrew Cooper
Dec 8, 2020    Waikoloa, HI (map)
20cm f/6 Newtonian, Cave Astrola @ 76x
Seeing: 6 Transparency: 7 Moon: 0%

A lovely quartet of stars at the center of M42 classically referred to as the Trapezium, four are obvious at 76x whith another marginally visible between A and B, all are white, seen in a cavity at the center of the nebula complex, the Trapezium is about 15" across, θ1Ori A and θ1Ori D are about equal at 7th magnitude at the eastern and western corners, while θ1Ori C is well over a magnitude brighter on the southern corner, and θ1Ori B a magnitude fainter at the northern corner

Captain William Henry Smyth
Jan 26, 1834    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A multiple star, the beautiful trapezium in the "Fish's mouth" of the vast nebula in the middle of Orion's sword-scabbard. A 6, pale white; B 7, faint lilac; C 7½, garnet; D 8, reddish; and E 15, blue.

This was entered 1 ♅. III., in November, 1776, and had the honour of being the object to which the grand forty-foot reflector was first directed, in February, 1787, under the designation of "quadruple." As a trapezium it was gazed at, measured, and delineated, for upwards of fifty years, when Σ. announced it "quintuplex," by the addition of the little star E. Now when we consider the eye of ♅., the measures of S., anil the rigorous examination of H., this little companion must be looked upon as variable; indeed nothing can exceed the confidence with which H. assured me, of its not being visible when he made the beautiful drawing of 1824, confirmed by himself and Mr. Ramage on the 3rd of March, 1826; and yet in 1828 it was not to be overlooked but by wilful inattention. Mr. Dawes afterwards saw it well with his five-foot telescope. The best measures for comparison with my epoch, are those of Σ. and S.; and by adjusting the latter's uncials and quadrants, they will stand thus:
           S. 1824.50               |          Σ. 1836.15
AB Pos. 310°48' Dist. 13".453 | Pos. 311°14' Dist. 12".983
AC 60°04' 13".582 | 60°07' 13".467
AD 345°03' 16".685 | 342°10' 16".780
BE (not seen) | 353°42' 3".860 (1832.53)
Ptolemy, Tycho Brahé, and Hevelius, ranked θ of the 3rd magnitude, as did Bayer in his Uranometria, all evidently supposing the two contiguous stars and the bright spot constituted a single star. The effulgent nebula in which it is placed, familiarly called the Fish's head, with its streaming appendages, certainly has an irregular resemblance to the head of some monster of the polyneme genus.

Its brilliancy is not equal throughout, but the glare of the brighter parts gives intensity to the darkness which they bound, and excites a sensation of looking through it into the luminous regions of illimitable space, a sensation not entirely owing to any optical illusion of contrast. This supposition must have forced itself upon Huygens, independently of any recollection of the empyrean heaven of the ancients; and had Voltaire seen the object under powerful means, he would hardly have lashed Dr. Derham for asking, whether nebube be not this shining region, seen through a chasm of the primum mobile. Another wonderful singularity is, that the nebulous and apparently attenuated matter seems to recede from the stars of the trapezium, so as to leave a black space around each, between them and the glow, as though they were either repelling or absorbing it.

This is a most splendid object under any telescope, but the greater the optical power applied, the more inexplicable does it become. My own telescope showed it to very great advantage, but it is here where the light-grasping quality of reflectors is brought advantageously to bear. Thus in the twenty-foot telescope at Slough, Sir John Herschel gained perceptions of its modification which were not decided to my view: "I know not," he says, "how to describe it better than by comparing it to a curdling liquid, or a surface strewed over with flocks of wool, or to the breaking up of a mackerel sky, when the clouds of which it consists begin to assume a cirrous appearance. It is not very unlike the mottling of the sun's disc, only, if I may so express myself, the grain is much coarser, and the intervals darker; and the flocculi, instead of being generally round, are drawn into little wisps. They present, however, no appearance of being composed of stars, and their aspect is altogether different from that of resolvable nebulas." Such, at present, are the only ascertained peculiarities of the wondrous mass. It is pronounced to be of the singular nature termed milky nebulosity by Sir William Herschel: "to attempt," he remarks, "even at a guess at what this light may be, would be presumptuous. If it should be surmised, for instance, that this nebulosity is of the nature of the zodiacal light, we should then be obliged to admit the existence of an effect without its cause. An idea of a phosphorical condition is not more philosophical, unless we could show from what source of phosphorical matter such immeasurable tracts of luminous phenomena could draw their existence, and permanency: for though minute changes have been observed, yet a general resemblance, allowing for the difference of telescopes, is still to be perceived in the great nebulosity of Orion, ever since the time of its first discovery." This illustrious astronomer was, at first, inclined to consider all the nebulae as resolvable, but this milky instance, with that in Andromeda, contradicted the notion, and led him to inferences respecting nebulous matter, and its possible gradation to stars by condensation, so as to form a distinct and plausible theory of cosmogony; with the originality of which neither the A'kásah., fifth element of the Brahmans, of which the heavens are formed, nor the vague notions of Tycho Brahé and Kepler, can properly be said to interfere. From these bold and almost overwhelming ideas we may yet become conscious, as well of the operations of the powerful agents by which whole systems are formed, as of those tremendous forces by which others are destroyed.

We are told that this nebula was one of the first fruits of Galileo's telescope; but it is certain that Huygens discovered it by accident in 1656, as stated in his Systema Saturnium. where he notes, "Portentum, cui certe simile aliud nusquàm apud reliquas fixas potuit animadverti." From a comparison of the descriptions and drawings of this object, since his time, great alterations might be inferred; but astronomical delineation was not then sufficiently advanced to render the diagrams at all satisfactory, nor were the instruments sufficiently powerful. Thus, while one man thinks his 3½ foot telescope indicated "myriads upon myriads " of stars in its composition, Lord Rosse, with the most powerful and perfect instrument extant, gained no appearance of re-solution. It may therefore be concluded, that the first rigidly accurate representation of it, is that by Sir John Herschel; and he who wishes to acquire all the actual knowledge we at present possess on the subject, cannot refer to a better description than that contained in his paper, published in the second volume of the Memoirs of the Astronomical Society. "Several astronomers," says Sir John, "on comparing this nebula with the figures of it handed down to us by its discoverer, Huygens, have concluded that its form has undergone a perceptible change; but when it is considered how difficult it is to represent such an object duly, and how entirely its appearance will differ even in the same telescope, according to the clearness of the air, or other temporary causes, we shall readily admit that we have no evidence of change that can be relied on." To the drawing which illustrates that account, posterity will refer with confidence, in order to "catch Nature in the fact:" meantime, it seems clear, that if the parallax of this nebula be no greater than that of the stars, as one hypothesis assumes, its breadth cannot be less than a hundred times that of the diameter of the Earth's orbit: but if, as is still more probable, at a vast distance beyond, its magnitude must be utterly inconceivable.

This luminous spot is so well known to all star-gazers, that it is hardly necessary to add, that a line projected from α Orionis, through ζ, the third of the belt, will pass upon θ and the nebula, in the sword-scabbard. The portion called the Fish's mouth, with the well-known trapezium, may be rudely sketched as in the preceding figure*.

θ2 Orionis, which is 133" from θ1 , on an angle = 135°, is coarsely double, of the 6th and 7th magnitudes. At the epoch above named, viz. 1834.07, the components measured 91°.5 as the angle of position, and 52" for the distance.
― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844
Other Data Sources for Trapezium
Associated objects for Trapezium
Nearby objects for Trapezium

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

A complete list of credits and sources can be found on the about page