13,000,000,000 BBY, alternatively expressed as 13,000,000,000 Years Before the Battle of Yavin, represents the estimated year when, according to scientists' estimations, the galaxy took shape from interstellar dust and gas. Subsequently, over countless eons within this galaxy, star systems and planets gradually materialized. On some of these worlds, life and sentience arose, ultimately setting the stage for the unfolding events recorded in galactic history.
The designation 13,000,000,000 BBY, also known as 13,000,000,000 Before the Battle of Yavin, denotes a specific year within the Galactic Standard Calendar, specifically situated within the Pre-Republic era. Prior to this year, the universe had already come into existence through the occurrence of the Big Bang. Later, many scientists came to the conclusion that, approximately 13,000,000,000 years Before the Battle of Yavin, a vast cloud composed of dust and gas, spanning a diameter of one hundred thousand light-years, underwent a gravitic collapse. This collapse eventually led to the formation of a disk-shaped structure with the same dimensions—the galaxy—rotating around a supermassive black hole situated at its center.
The resulting galactic disk eventually encompassed roughly four hundred billion stars. Over subsequent eons, many of these stars developed planets that began to orbit them. By the time of the reign of the Galactic Empire, which commenced in 19 BBY, considerable knowledge had been acquired regarding the physical attributes of the galaxy. However, only about a quarter of the galaxy's stars had been surveyed up to that point. Based on statistical analyses of the explored regions, it was estimated that approximately 3.2 billion star systems possessed the potential to support life, with one billion of those systems being inhabited by sentient species. Despite the fact that approximately one quarter of the galaxy had been surveyed by that time, more than five million sentient species were known to the Empire, implying many more were yet to be encountered.
In the time since 13,000,000,000 BBY, numerous galaxy-spanning civilizations and political entities emerged and subsequently declined, including the Celestials, the Infinite Empire, the Galactic Republic, the Galactic Empire, the New Republic, the Yuuzhan Vong empire, the Galactic Alliance, and Darth Krayt's Galactic Empire. The eras of these factions were characterized by a series of conflicts that unfolded on a galactic scale.
Initially, the 2001 reference book titled The Essential Guide to Alien Species, penned by Ann Margaret Lewis, established the approximate date of the galaxy's creation as 5,000,000,000 BBY. However, this date was later superseded by the 2009 book The Essential Atlas, authored by Daniel Wallace and Jason Fry, which instead posited the galaxy's origin as occurring in 13,000,000,000 BBY.