Page:Sir William Herschel, his life and works (1881).djvu/230

208 So, at first, believed that his twenty-foot telescope was of power sufficient to fathom the Milky Way, that is, to see through it and beyond it, and to reduce all its nebulosities to true groups of stars.

In 1791 he published a memoir on Nebulous Stars, in which his views were completely changed. He had found a nebulous star, the sixty-ninth of his Class IV., to which his reasons would not apply. In the centre of it was a bright star; around the star was a halo gradually diminishing in brightness from the star outward, and perfectly circular. It was clear the two parts, star and nebula, were connected, and thus at the same distance from us.

There were two possible solutions only. Either the whole mass was, first, composed of stars, in which case the nucleus would be enormously larger than the other stars of its stellar magnitude elsewhere in the sky, or the stars which made up the halo indefinitely small; or, second, the central nucleus was indeed a star, but a star surrounded with "a shining fluid, of a nature totally unknown to us."