|
Nebula - LoveToKnow 1911 (1858 words) |
 | An enumeration of nebulae was made by Charles Messier in Paris in 1771, who recorded 103; Sir William Herschel increased the number known to over 250o; whilst Sir John Herschel between 1825 and 1847 catalogued and described 3926 nebulae (including 1700 observed at the Cape of Good Hope). |
| Nebulae may be conveniently classified according to their telescopic appearance; we enumerate below some of the principal forms that have been recognized, but it must be observed that this classification is rather superficial, and that the differentiation is often one of appearance only and not of real structure. |
| The typical spiral nebulae are in the form of a double spiral, the two branches of which proceed from diametrically opposite points of a bright nucleus and wind round it in the same sense; the whole is generally studded with points of condensation. |
| nebula. The Columbia Encyclopedia, Sixth Edition. 2001-07 (415 words) |
| In 1864, William Huggins confirmed William Herschel’s conclusion that nebulae are not swarms of stars by determining that the spectra of nebulae are made of bright lines characteristic of radiating gases. |
| Some bright nebulae, composed primarily of hydrogen gas ionized by nearby hot blue-white stars, radiate their own light; they are called emission nebulae and are characterized by narrow spectral emission lines. |
| Dark nebulae are detected as empty patches in a field of stars or as dark clouds obscuring part of a bright nebula in the background, as in the case of the Horsehead Nebula. |
Feeds |
Contact