Magellanic Clouds

The two Magellanic Clouds (or Nubeculae Magellani), composed of the Large Megellanic Cloud and the Small Magellanic Cloud, are irregular dwarf galaxies visible in the southern hemisphere. They are members of our Local Group and orbit the Milky Way galaxy.

Persian astronomer Al Sufi, in 964, was the first to have written anything about the Magellanic Clouds proving they have been known since early time amongst the Middle East peoples. Sufi, in his Book of Fixed Stars, calls the clouds al-bakr, meaning “the Sheep”. Italian Peter Martyr and Andreas Corsali were the first to observe the Clouds in Europe at the end of the 15th Century. Antonio Pigafetta reported the Clouds for Ferdinand Magellan’s expedition however the naming of the clouds after Magellan did not become widespread until later.

The Clouds look like separate pieces of the Milky Way to the naked eye and both the Large and Small Cloud can be seen in the Southern Hemisphere. Until the Sagittarius Dwarf Elliptical Galaxy was discovered in 1994 the Clouds were the closest known galaxies to our own and were roughly 75,000 light- years apart from each other. The LMC lies about 40,000 miles closer to us and some might think that it appears larger since it is closer, however, it is about twice the size of the SMC.

Since the Clouds travel so closely to the Milky Way there is theoretical evidence that suggests the Clouds have both been distorted by the tidal interaction between the clouds and the Milky Way. However, their gravity has also affected the Milky Way causing distortion on the outer parts of the galactic disk. The Clouds have two major differences from our galaxy. The first is that they have a higher fraction of their mass composed of hydrogen and helium. Second, they have a lot less metals than the Milky Way. The youngest stars in the LMC and SMC have a metallicity of 0.5 and 0.25 times solar, respectively. Like out own Galaxy, their stars range from very you to very old indicating a long stellar formation but are generally noted for their nebulae and young stellar populations.

The Large Magellanic Cloud was host galaxy to a supernova (SN 1987A), the brightest observed in over three centuries.

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