<P> The satellite galaxies surrounding the Milky way are not randomly distributed, but seemed to be the result of a break - up of some larger system producing a ring structure 500,000 light years in diameter and 50,000 light years wide . Close encounters between galaxies, like that expected in 4 billion years with the Andromeda Galaxy rips off huge tails of gas, which, over time can coalesce to form dwarf galaxies in a ring at right angles to the main disc . </P> <P> The Milky Way and the Andromeda Galaxy are a binary system of giant spiral galaxies belonging to a group of 50 closely bound galaxies known as the Local Group, surrounded by a Local Void, itself being part of the Virgo Supercluster . Surrounding the Virgo Supercluster are a number of voids, devoid of many galaxies, the Microscopium Void to the "north", the Sculptor Void to the "left", the Bootes Void to the "right" and the Canes - Major Void to the South . These voids change shape over time, creating filamentous structures of galaxies . The Virgo Supercluster, for instance, is being drawn towards the Great Attractor, which in turn forms part of a greater structure, called Laniakea . </P> <P> Two smaller galaxies and a number of dwarf galaxies in the Local Group orbit the Milky Way . The largest of these is the Large Magellanic Cloud with a diameter of 14,000 light - years . It has a close companion, the Small Magellanic Cloud . The Magellanic Stream is a stream of neutral hydrogen gas extending from these two small galaxies across 100 ° of the sky . The stream is thought to have been dragged from the Magellanic Clouds in tidal interactions with the Milky Way . Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf . The smallest dwarf galaxies of the Milky Way are only 500 light - years in diameter . These include Carina Dwarf, Draco Dwarf, and Leo II Dwarf . There may still be undetected dwarf galaxies that are dynamically bound to the Milky Way, which is supported by the detection of nine new satellites of the Milky Way in a relatively small patch of the night sky in 2015 . There are also some dwarf galaxies that have already been absorbed by the Milky Way, such as Omega Centauri . </P> <P> In 2014 researchers reported that most satellite galaxies of the Milky Way actually lie in a very large disk and orbit in the same direction . This came as a surprise: according to standard cosmology, the satellite galaxies should form in dark matter halos, and they should be widely distributed and moving in random directions . This discrepancy is still not fully explained . </P>

What are the clouds in the milky way