The Magellanic Clouds (or Nubeculae Magellani) are two irregular dwarf galaxies visible in the Southern Celestial Hemisphere; they are members of the Local Group and are orbiting the Milky Way galaxy. Because both show signs of a bar structure, they are often reclassified as Magellanic spiral galaxies.
The Magellanic Clouds have been known since ancient times by indigenous people from South America and Africa, and from the first millennium in Western Asia. The first preserved mention of the Large Magellanic Clouds is believed to be in petroglyphs and rock drawings found in Chile.
The Large Magellanic Cloud and its neighbour and relative, the Small Magellanic Cloud, are conspicuous objects in the southern hemisphere, looking like separated pieces of the Milky Way to the naked eye. Roughly 21° apart in the night sky, the true distance between them is roughly 75,000 light-years. Until the discovery of the Sagittarius Dwarf Elliptical Galaxy in 1994, they were the closest known galaxies to our own (since 2003, the Canis Major Dwarf Galaxy was discovered to be closer still, and is now considered the actual nearest neighbor). The LMC lies about 160,000 light years away, while the SMC is around 200,000. The LMC is about twice the diameter of the SMC (14,000 ly and 7,000 ly respectively). For comparison, the Milky Way is about 100,000 ly across.
Aside from their different structure and lower mass, they differ from our galaxy in two major ways. First, they are gas-rich; a higher fraction of their mass is hydrogen and helium compared to the Milky Way. They are also more metal-poor than the Milky Way; the youngest stars in the LMC and SMC have a metallicity of 0.5 and 0.25 times solar, respectively. Both are noted for their nebulae and young stellar populations, but as in our own galaxy their stars range from the very young to the very old, indicating a long stellar formation history.
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