Large Magellanic Cloud

The Large Magellanic Cloud (LMC), or Nubecula Major is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (~16 kpc) and the possible dwarf irregular galaxy known as the Canis Major Overdensity. Based on readily visible stars and a mass of approximately 10 billion solar masses, the diameter of the LMC is about 14,000 light-years (4.3 kpc). It is roughly a hundredth as massive as the Milky Way and is the fourth-largest galaxy in the Local Group, after the Andromeda Galaxy (M31), the Milky Way and the Triangulum Galaxy (M33). The Milky Way and the LMC are predicted to merge in approximately 2.4 billion years.
== History of observation ==
Both clouds have been easily visible for southern nighttime observers well back into prehistory. It has been claimed that the first-known written mention of the Large Magellanic Cloud was by the Persian astronomer 'Abd al-Rahman al-Sufi Shirazi (later known in Europe as "Azophi"), in his Book of Fixed Stars around 964 AD. However, this seems to be a misunderstanding of a reference to some stars south of Canopus which he admits he has not seen. The first confirmed recorded observation was in 1503–1504 by Amerigo Vespucci in a letter about his third voyage. He mentioned "three Canopes [sic], two bright and one obscure"; "bright" refers to the two Magellanic Clouds, and "obscure" refers to the Coalsack.
Measurements with the Hubble Space Telescope, announced in 2006, suggest the Large and Small Magellanic Clouds may be moving too quickly to be orbiting the Milky Way. Astronomers discovered a new black hole inside the Large Magellanic Cloud in November 2021 using the European Southern Observatory's Very Large Telescope in Chile. Astronomers claim its gravity is influenced by a nearby star, which is about five times the mass of our Sun.
== Geometry and distance ==
The Large Magellanic Cloud has a prominent central bar and spiral arm. The central bar seems to be warped so that the east and west ends are nearer the Milky Way than the middle. In 2014, measurements from the Hubble Space Telescope made it possible to determine a rotation period of 250 million years.
Distance to the LMC has been calculated using standard candles; Cepheid variables are one of the most popular. These have been shown to have a relationship between their absolute luminosity and the period over which their brightness varies. However the variable of metallicity may also need to be taken as a component of this as consensus is this likely affects their period-luminosity relations. Unfortunately, those in the Milky Way typically used to calibrate the relation are more metal-rich than those found in the LMC. Modern 8-meter-class optical telescopes have discovered eclipsing binaries throughout the Local Group. Parameters of these systems can be measured without mass or compositional assumptions. The light echoes of supernova 1987A are also geometric measurements, without any stellar models or assumptions.
Category:Galaxies