Milky Way galaxy - Milky Way galaxy: The Milky Way galaxy, more commonly known as the "Milky Way," or just "the galaxy," is the galaxy that Mankind calls home and in which the Imperium of Man and all of the other starfaring intelligent species known to Humanity are located. The Milky Way is a barred spiral galaxy that is part of the Local Group of galaxies.It is one of hundreds of billions of galaxies in the observable universe. Its name is a translation of the Latin term Via Lactea, in turn translated from the Greek galaxias, referring to the pale band of light formed by stars in the galactic plane as seen in the night skies of Holy Terra.Some sources hold that, strictly speaking, the term "Milky Way" should refer exclusively to the band of light that the galaxy forms in the Terran night sky and the skies of many other settled planets, while the galaxy should receive the full name "Milky Way galaxy," or alternatively "the galaxy." However, it is unclear how widespread this convention is, and the term "Milky Way" is routinely used in either context.The stellar disk of the Milky Way galaxy is approximately 100,000 light-years in diameter, and is considered to be, on average, about 1,000 light years thick. It is estimated to contain at least 200 billion stars and possibly up to 400 billion stars with an estimated average of 300 billion, the exact figure depending on the number of very low-mass, or dwarf stars. This can be compared to the one trillion stars of the larger neighbouring Andromeda galaxy.The stellar disc does not have a sharp edge, a radius beyond which there are no stars. Rather, the number of stars drops smoothly with distance from the centre of the galaxy. Beyond a radius of roughly 40,000 light years from the galactic centre, the number of stars drops much faster with radius, for reasons that are not understood.Extending beyond the stellar disk is a much thicker disk of gas. The gaseous disk at the centre of the Milky Way has a thickness of around 12,000 light years. The Galactic Halo extends outward, but is limited in size by the orbits of two Milky Way satellite galaxies, the Large and the Small Magellanic Clouds, whose perigalacticon is at about 180,000 light years. At this distance or beyond, the orbits of most halo objects would be disrupted by the Magellanic Clouds, and the objects would likely be ejected from the vicinity of the Milky Way.Following the birth of the Chaos God Slaanesh at the end of the Age of Strife in the early 30th Millennium A.D., the galaxy was rent by the implosion of the Aeldari Empire. Where the core worlds of that ancient stellar realm had been in the galactic northwest, a vast new Warp rift spilled out into realspace -- the Eye of Terror, originally classified as stellar anomaly "Cygnus X-1" by Imperial astrographers.The strains on the fabric of local space-time created by Slaanesh's birth in the Immaterium also weakened the barriers between the Warp and realspace across the galaxy. The result was the creation of smaller, permanent Warp rifts across the Milky Way beyond the Eye of Terror, including such anomalies as the Maelstrom. At the same time, Warp storms grew in size and frequency across the galaxy in the ten thousand Terran years since the birth of the Eye of Terror.These strains reached a breaking point following the fall of the Fortress World of Cadia to the Chaos forces of Abaddon the Despoiler's 13th Black Crusade in ca. 999.M41. In the wake of the destruction of Cadia and the Necron-built Cadian Pylons on that world that had long kept the growth of the Eye of Terror in check, the Cadian Gate was overwhelmed by the forces of Chaos, and the Eye of Terror actually began to expand across the galaxy.Eventually, the galaxy was bisected by a massive new Warp rift called the Great Rift, or Cicatrix Maledictum, spreading from its heart in the Eye of Terror all the way to the Hadex Anomaly of the Jericho Reach in the Eastern Fringe of the galaxy. This change marked the start of a new epoch in Human history known as the Era Indomitus.To those on the Terran side of the rift, it is a tainted scar stretching across the sky. To those unfortunates on the far side, it is something much worse -- the very gates of Hell. There, the light of the Emperor's Astronomican is obscured behind a psychic maelstrom of nightmares and the entire region has been dubbed the Imperium Nihilus, or the Dark Imperium. The half of Imperial space near to Terra where the light of the Astronomican still shines is called the Imperium Sanctus.