The Magellanic Clouds are a pair of nearby galaxies which are visible from the Southern hemisphere: the Large Magellanic Cloud, and the Small Magellanic Cloud. The oldest Middle Eastern astrological writings refer to these regions of the sky, but they were not given the name Magellan until the 1500s. Both are about 200,000 light-years from the Earth.
– Relationship to the Milky Way Galaxy –
The Magellanic Clouds are the closest galaxies to our own Milky Way. Both have much denser gas concentrations (which gives them their noticeable cloudy appearance), and both are home to stars with much higher concentrations of hydrogen and helium than those in our own Galaxy. Both are also classified as irregular galaxies; perhaps because of their interaction with the Milky Way Galaxy, they do not resemble the usual galaxy forms of either a spiral or an ellipsis.
Both, however, are also considerably smaller than the Milky Way: even the Large Magellanic Cloud is just a tenth the size of the Milky Way. As a result, our galaxy’s much more powerful gravity is gradually tugging the Clouds apart. Detectable streams of hydrogen gas, for example, are being pulled away from the Magellanic Clouds and pulled down into the Milky Way. Until recently astronomers believed that the Clouds were small enough to be actually orbiting the Milky Way, but new measurements of their velocity suggest that they are not orbiting us, just travelling close by. They are still classified as members of the Local Group of galaxies.
– Large Magellanic Cloud –
The Large Magellanic Cloud is the larger of the two galaxies, containing perhaps ten billion stars and spanning 14,000 light-years across. It possesses a single spiral arm, compared to the multiple arms of the Milky Way, and is located about 160,000 light-years from the Earth.
The Cloud is unusually rich in free-floating hydrogen, which means that – at least at present – it creates stars very rapidly, and thus holds many interests for astronomers. These include the beautiful Tarantula Nebula, a massive, 1000-light-year-wide region containing 450,000 times the mass of our own Sun. Astronomers believe stars are being born within the Tarantula Nebula more quickly than any other region of space in the Local Group of galaxies. In 1987, a supernova which exploded within the Tarantula Nebula, the brightest observed supernova in the modern history of astronomy.
– Small Magellanic Cloud –
The Small Magellanic Cloud is the smaller of the two galaxies, containing only about seven billion stars and spanning 7,000 light-years across. It contains a central bar-shaped band of stars, and no spiral arms, unlike the Milky Way or the Large Magellanic Cloud. It is 200,000 light-years from the Earth, but can still be easily seen with the unaided human eye from the southern hemisphere and the equator.
