Magellanic Clouds

Magellanic Clouds , 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.

Magellanic Clouds The two irregular galaxies that are satellites of our own Galaxy, easily seen with the naked eye in the southern hemisphere like detached portions of the Milky Way. They are named after the Portuguese explorer Ferdinand Magellan (1480–1521), who described them during his voyage around the world. Both Clouds are believed to orbit our Galaxy in a plane nearly perpendicular to its disk, and may eventually spiral into the Galaxy. See also Large Magellanic Cloud; Magellanic Stream; Small Magellanic Cloud.

magellanic clouds, a popular name for the two nebiculae, or cloudy-looking areas in the southern sky, which comprise a great number of small stars much resembling the Milky Way. They were named after Ferdinand Magellan.