Certain stars and nebulae show a bright line helium spectrum.
He arranges a selection from his observations on the nebulae in such a way as to give great plausibility to his view of the gradual transmutation of nebulae into stars Herschel begins by showing us that there are regions in the heavens where a faint diffused nebulosity is all that can be detected by the telescope.
Thus in 1864 the spectroscope yielded him evidence that planetary and irregular nebulae consist of luminous gas - a conclusion tending to support the nebular hypothesis of the origin of stars and planets by condensation from glowing masses of fluid material.
It does not, however, seem probable that their apparent anti-galactic tendency has such a significance; in the Magellanic Clouds spiral nebulae are very abundant, a fact which shows that there is no essential antipathy between the stars and the spiral nebulae.
There are other nebulae in which a nucleus can be just discerned, others again in which the nucleus is easily seen, and still others where the nucleus is a brilliant star-like point.
Should any one be sceptical as to the sufficiency of these laws to account for the present state of things, science can furnish no evidence strong enough to overthrow his doubts until the sun shall be found growing smaller by actual measurement, or the nebulae be actually seen to condense into stars and systems."
By this means she detected in 1783 three remarkable nebulae, and during the eleven years 1786-1797 eight comets, five of them with unquestioned priority.
Though she returned to Hanover in 1822 she did not abandon her astronomical studies, and in 1828 she completed the reduction, to January 1800, of 2500 nebulae discovered by her brother.
He intended to follow it up with similar treatises on Mars, Jupiter, sun, moon, comets and meteors, stars, and nebulae, and had in fact commenced a monograph on Mars, when the failure of a New Zealand bank deprived him of an independence which would have enabled him to carry out his scheme without anxiety as to its commercial success or failure.
Of these the more noteworthy dealt with the distribution of stars, starclusters and nebulae, and the construction of the sidereal universe.
Owing to the famine and the disturbed state of the country, which demanded his attention as a large landowner and lieutenant of King's County (from 1831), the instrument remained unused for nearly three years, but since 1848 it has been in constant use, chiefly for observations of nebulae, for which it was particularly suited on account of its immense optical power, nominally 6000.
In the same publication for 1844 and 1850 he communicated short descriptions and drawings of some of the more interesting nebulae, and in the volume for 1861 he published a paper "On the Construction of Specula of 6-ft.
Aperture, and a Selection from the Observations of Nebulae made with them," with numerous engravings.
Among his contributions to astronomy may be noted his eleven zonecatalogues of 34,674 stars, his measurements, in 1836-1837, of nebulae and clusters, and his determination of the mass of Uranus from observations of its satellites (Mena.
Precht, Ber., 1886, 19, p. 2326), in some meteorites, in certain stars and nebulae, and also in the envelopes of the sun.
But at the same time none but the Herschels have swept the whole sky for the discovery of faint nebulae; and FIG.
(3) As a Cassegrain reflector, for photographing the moon, planets or very bright nebulae on a large scale, as shown in fig.
Doubtless with improved telescopes many more apparent nebulae would be shown to be clusters, but there are certainly many nebulae which are otherwise constituted.
This may explain the existence of gaseous nebulae, which are often found intimately associated with star-clusters, a good example being the nebulosity surrounding the Pleiades.
Spiral nebulae have the remarkable characteristic of avoiding the galactic plane, and it has been suggested that the space outside the limits of the stellar universe is filled with them.
At the present day when the nebulae that are spiral in form have been shown to be so numerous, next to the fixed stars themselves, our view of the nebular theory has been somewhat modified.
Photographs of Nebulae; Sir Robert Ball, The Earth's Beginning.
The accounts of the observations given in these papers, however, were fragmentary; but in 1879-80 a complete account of them was published by the present earl ("Observations of Nebulae and Clusters of Stars made with the 6-foot and 3-foot Reflectors at Birr Castle from 1848 to 1878") in the Scient.
The stars are supposed to be generally spherical, like the sun, in form, and to have fairly well-defined boundaries; while the nebulae are generally irregular in outline and have no well-defined limits.
Charles Messier (1730-1817) had catalogued in 1781 103 nebulae; Herschel discovered 2500, laid down the lines of their classification, divined the laws of their distribution, and assigned their place in a scheme of development.
Sions be secured of such faint objects as nebulae, tele scopic comets, and the immense majority of stars, or of the dim ranges of stellar and nebular spectra.
There are many lines in the spectra of the stars, as well as of the nebulae, which are not certainly identified with those belonging to any elements known to our chemistry.
The question is rather that of the infinity of forms that matter may assume, including that most attenuated form found in the nebulae, which seem to be composed of matter more refined than even the atoms supposed to make up the matter around us.
2 All the time-worn fables and conjectures regarding the composition of the Milky Way were at once dissipated by the simple statement that to the eye, reinforced by the telescope, it appeared as a congeries of lesser stars, while the great nebulae were equally declared to be resolvable into similar elements.
