Magellanic clouds are two small galaxies that orbit our Milky Way galaxy. They are called the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). The LMC is about 160,000 light-years away from us, while the SMC is about 200,000 light-years away.
The first recorded mention of the Magellanic Clouds was by the Greek philosopher Aristotle in 350 BC. He thought they were clouds in Earth’s atmosphere. In 1493, Christopher Columbus mentioned them in his journal while sailing near South America. He thought they were a sign that land was nearby. However, it wasn’t until 1826 that Polish astronomer Joachim Mallet correctly identified them as distant galaxies.
In addition to being close to each other and to our Milky Way galaxy, the LMC and SMC have some other similarities. They are both irregularly shaped galaxies with lots of young stars and star-forming regions. They also both contain giant molecular clouds—large reservoirs of dense gas where new stars can form.
The two Magellanic Clouds are not identical twins, however. The LMC is much more massive than the SMC—about 10 times more massive, in fact. It also has a higher number of old stars and globular clusters (collections of hundreds of thousands or even millions of stars that orbit a galaxy’s center).
The LMC is so massive that its gravity affects our own Milky Way galaxy! As the LMC orbits around us, its gravity pulls on our galaxy’s gas and dust lanes, distorting their shape. The most famous example of this effect is “the stream”—a long ribbon of gas stretching from our galaxy all the way to the LMC that was pulled off by the LMC’s gravity during one of its past passages by us