History Of The Orion Nebula

In 1610, two years after the invention of the telescope, the Orion Nebula, which looks like a star to the naked eye, was discovered by a scholar named Nicolas-Claude Fabri Peiresc. In 1656 Christan Huygens, the Dutch scholar and scientist, using his own greatly improved instruments, was the first to describe the inner region of the nebula, and to determine that its inner star is not single but a compact quadruple system.

Early 18th-century observational astronomers gave high priority to comet seeking. A by-product of their search was the discovery of many bright nebulae. Several catalogs of special objects were compiled by comet researchers; by far the best known is that of the Frenchman Charles Messier, who in 1781 compiled a catalog of 103 nebulous, or extended, objects in order to prevent their confusion with comets. Most are clusters of stars, 35 are galaxies, and 11 are nebulae. Even today many of these objects are commonly referred to by their Messier Catalog number; M20, for instance, is the great Trifid Nebula, in the constellation Sagittarius.

THE WORK OF THE HERSCHELS

By far the greatest observers of the early and middle 19th century were the English astronomers William Herschel and his son John. Between 1786 and 1802 William Herschel, aided by his sister Caroline, compiled three catalogs totaling about 2,500 clusters, nebulae, and galaxies. John Herschel later added to the catalogs 1,700 other nebulous objects in the southern sky visible from the Cape Observatory in South Africa but not from London and 500 more objects in the northern sky visible from England.

The catalogs of the Herschels formed the basis for the great New General Catalogue (NGC) of J.L. Dreyer, published in 1888. It contains the location and a brie...

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...ry high spectral resolution (i.e., to distinguish slightly differing wavelengths). For even higher spectral resolution astronomers employ Fabry-Perot interferometers. Spectra provide powerful diagnostics of the physical conditions within nebulae. Images and spectra provided by Earth-orbiting satellites, especially the Hubble Space Telescope, have yielded data of unprecedented quality.

Ground-based observations also have played a major role in recent advances in scientific understanding of nebulae. The emission of gas in the radio and submillimetre wavelength ranges provides crucial information regarding physical conditions and molecular composition. Large radio telescope array's, in which several individual telescopes function collectively as a single enormous instrument, give spatial resolutions in the radio regime far superior to any yet achieved by optical means.