Page:Popular Science Monthly Volume 38.djvu/353

 of origin of the many curious streams and chains of stars with which the heavens abound, when we look at another amazing revelation of celestial photography. I refer to Prof. Pickering's photograph of Orion, taken with a portrait-lens from a mountain in southern California.

In this photograph a tremendous spiral nebula is revealed, covering a space on the sky fifteen degrees in diameter, and embracing the whole of the constellation with the exception of the head and shoulders and the upraised arms of the imaginary giant. The well-known nebula in the Sword, the three bright stars in the Belt, the brilliant first-magnitude star Rigel, together with its less splendid neighbor Beta of Eridanus, and Kappa Orionis, forming the lower left-hand corner of the great quadrilateral of Orion—are all included within the boundaries of this vast nebula. The nebula in the Sword is seen to be only an exceptionally bright condensation in the nebulous system surrounding it.

But for our purposes the thing to be particularly noticed is the arrangement of the stars within the nebula. Any one who has viewed Orion with a powerful opera or field glass must have been struck with the curious marshaling of many of the smaller stars. This is particularly noticeable around the Belt, where the star Epsilon, itself long known to be enmeshed in a faint nebula, is environed with a garland of little stars., which, defiling in a beautiful double curve, finally stop near Delta, the next star above in the Belt. But, indeed, one does not need a glass in order to perceive similar rows of stars in Orion. The most conspicuous of these, after the three stars in the Belt themselves, are those that outline the giant's left arm and the lion's skin that he is supposed to bear upon it. Another row, not so striking, is, however, more interesting just at this point, because it follows the curve of the great outer spiral of the newly discovered nebula. This file of stars really begins below the Belt at Eta, and, curving round between the Belt and Gamma or Bellatrix in the left shoulder, includes the stars 27, 22, Ψ1,Ψ2, 33, 38, and ω, besides others too faint to be visible to the unassisted eye. The connection between these stars and the nebula seems too evident to be doubted. The spiral form of the latter furnishes an explanation