Magellanic Clouds (redirected from Clouds of Magellan)

Magellanic Clouds (măj'əlăn`ĭk), two dwarf galaxies located in the far southern sky and visible to the unaided eye; they are classified as irregular because they show no definite symmetry or nucleus. The larger of the two, known as the Large Magellanic Cloud (LMC), is located mostly in the constellation Dorado; its angular diameter measures approximately 7°. The Small Cloud (SMC) is almost completely in the constellation Tucana, and measures approx. 4° in diameter. Both are nearly 160,000 light-years from the earth. They are part of the Local Group of galaxies, which includes our own galaxy (the Milky Way) and the Andromeda Galaxy, and are the nearest extragalactic objects. The Magellanic Clouds, named for the Portuguese navigator Magellan, were first studied in detail by Sir John Herschel in the 19th cent. While studying Cepheid variable stars in the SMC, Henrietta Leavitt discovered (1912) the period-luminosity relation. This relation offered a technique for measuring the distances of stars and galaxies. In Feb., 1987, Supernova 1987A erupted in the LMC. The first supernova visible without a telescope since 1604, this star gradually brightened over the next few months and remains under careful observation as it fades. The diffuse nebulae in both the LMC and the SMC appear to have fewer "metals" (elements heavier than helium); the deficiency is much more pronounced in the SMC.

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Magellanic Clouds [¦maj·ə¦lan·ik ′klau̇dz]

(astronomy)

Two irregular clouds of stars that are the nearest galaxies to the galactic system; both the Large and Small Magellanic Clouds are identified as Irregular in the classification of E.P. Hubble. Also known as Nubeculae.

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Magellanic Clouds 

(Large and Small Magellanic Clouds), two stellar systems (galaxies) of irregular shape, the nearest stellar systems to our stellar system, the Milky Way Galaxy, which includes the sun. The Magellanic Clouds are visible to the unaided eye from the southern sky in the form of nebulous patches; the Clouds are not visible in the middle latitudes of the northern hemisphere. They are called the Magellanic Clouds because their discovery is attributed to one of the members of the voyage around the world led by F. Magellan (1519-22).

The Large Magellanic Cloud is located in the constellation Dorado, and the Small Magellanic Cloud in the constellation Tucana. The distance to both Magellanic Clouds from the sun has been determined from observations of the many cepheid variable stars. Data on the Magellanic Clouds are given in Table 1.

Table 1. Data on Magellanic Clouds
	Large Magellanic Cloud	Small Magellanic CloudCloud
Distance from sun (kpc)............	55	55
Diameter (kpc)............	˜6.9	˜3.5
Apparent diameter......... . .	˜7°	˜4°
Absolute Photographic stellar magnitude ............	-18.1	-16.2

The Magellanic Clouds contain an extremely large number of star clusters, gaseous nebulae, different types of variable stars, and other objects. The star S Doradus, whose photographic luminosity is 120,000 times greater than that of the sun, is found in one of the star clusters of the Large Magellanic Cloud. The Large Magellanic Cloud also contains the giant gaseous nebula 30 Doradus (the Looped Nebula). If this nebula were located at the same distance from Earth as the Orion Nebula (300 parsecs), then objects on the earth illuminated with its light would have observable shadows.