Abstract
A SHORT time ago we gave an abstract of d'Arrest's “spectroscopical researches.” The Danish paper contains also the conclusions at which he arrived after many years contemplation of the nebula in the sword-handle of Orion. The spectrum is now easily visible, with open slit, even without a telescope. Then we see three images of the nebula corresponding to the three lines, whose relative intensity d'Arrest found to be 100, 24, and 71. To see the fourth line is of course very difficult. If the spectrum of the stars is looked at together with that of the nebula, we find the nebular lines continue absolutely unimpaired through the inner trapeze. Consequently it cannot be considered as proved that the stars are in connection with the nebula. It has not, of course, yet been possible to ascertain spectroscopically whether the stars are nearer to us than the nebula, or farther away in space. The question of resolvability has lost a good deal in interest since Huggins showed its gaseous nature. However, d'Arrest would not believe that it had ever been resolved into stars in any of the large telescopes of his day. All the more startling was the Rev. Dr. Robinson's letter (NATURE, vol. xv. p. 292), that he as early as 1848 had resolved this nebula with the Earl of Rosse's telescopes. It would be worth while for Mr. Ellery, who, according to our astronomical column, is investigating the southern nebulas, to ascertain whether actual resolvability is referred to here, or the circumstance that, as might be expected in so enormous a reflector, a good many small stars become visible by glimpses. Liapounov describes the appearance of Regio Hugeniana as follows: “Ces masses m'avaient présenté à plusieurs occasions des ressemblances frappantes avec des amas d'étoiles. Le caractère stellaire s'est prononcé d'abord dans la masse la plus lumineuse, dont l'apparence me conduisait depuis constamment à l'idée d'une agglomération de petites étoiles condensées.” We are hardly right in concluding that the nebula could be resolved in the nine-inch refractor of the Cazan observatory.
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D., W. THE ORION NEBULA . Nature 18, 313–315 (1878). https://doi.org/10.1038/018313b0
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DOI: https://doi.org/10.1038/018313b0