Nebulae

Nebulae are bright patches seen in the sky, consisting either of far-distant stars or of matter in a less condensed state. The number of nebula; known before Sir W. Herschell's time was only about 100, but by using a better telescope he increased the number to about 2,000. The great improvement in telescopes has enabled more and more of these nebulas to be resolved into clusters of stars, and it is supposed that, if the power of telescopes could be increased to any extent, all nebulae could be so resolved. Nebulas vary greatly in form and appearance; some are clearly clusters of stars, others are perfectly hazy. A round or oval form is sometimes exhibited, with a gradual condensation towards the centre, and a number of stars standing in the centre of a nebulous haze can be observed. Observations on nebulas caused Kant and Laplace to suggest a theory - now known as the nebular theory - as to the formation of worlds. They considered that the solar system, for example, originally existed as uncondensed nebulous matter. This gradually condensed towards the centre, forming the nucleus of the sun, and later the outer parts separated into distinct parts, each part condensing into a planet. The different forms of nebulas observed in the heavens were then supposed to be systems in different stages of development. Although instruments, such as Lord Rosse's telescope, have shown that so many nebulas can be resolved into star clusters, yet, on the other hand, the spectroscope has shown us that many nebulas do really consist of uncondensed matter.