13 , 000 , 000 , 000 BBY 13 , 000 , 000 , 000 Before the Battle of Yavin was the approximate year , firmly in the Pre - Republic era , in which it was believed that the galaxy was formed from universal debris . Over the ensuing eons , star systems and planets formed within the galaxy , with life and sentience growing upon these worlds ' surfaces , leading to the events of galactic history . The galaxy in 13 , 000 , 000 , 000 BBY . By the year 13 , 000 , 000 , 000 BBY , long before the Galactic Republic was founded , the Big Bang had already taken place , creating the universe . Many believed that it was approximately the year in which a cloud of dust and gas within the universe that was one hundred thousand light year s across experienced a gravitic collapse ; the cloud coalesced to form a disk of the same dimension that revolved around an extremely massive black hole , the galaxy . Impact . The galactic disk came to have three vertical layers : one in the middle that was 2 , 000 light years thick called the " thin slice " sandwiched between two 3 , 500 light year sections on either side of that called the " thick slice . " The majority of the galaxy ' s approximately four hundred billion stars fell within the thin slice , though the thick slice had some , and there was also a great sphere around the galactic disk called the " stellar halo " that consisted of billions of stars with highly elliptical orbits . Many of the stars ended up developing planets that orbited them over the succeeding eons . Half of these star systems — primarily within the thin slice — maintained conditions favorable to life , ten percent of this half actually developed life , and only one in a thousand of the life - bearing worlds went on to bear true sentience . Life would still be emerging on planets in the galaxy by 5 , 000 , 000 , 000 BBY . Many of these forms of sentience would try to explain their conditions , forming religions . A number developed creation myths , detailing how their existence came to be , whether that meant the creation of the galaxy , the formation of their world , or the origin of life . The Mandalorian religion had a creation tale called the " Akaanati ' kar ' oya " , " The War of Life and Death " in Basic , and it posited that the stars in the sky were ancient Mandalorian leaders that had died . Life that grew on worlds separated by great distances , primarily twenty million sentient species , would go on to interact and integrate , experiencing and eventually recording galactic history . By the reign of the Galactic Empire , which began in 19 BBY , much would be known about the physical properties of the galaxy , from its stars to its planets , but only about a quarter of all stars in the galaxy were surveyed . Contemporary estimates stated that of all the stars , 7 . 1 billion were not dangerous to life while 3 . 2 billion of those supported actual star systems — it was proposed that at least one billion of them were inhabited to some degree , and Imperial census data showed 69 million that were populated significantly . There were 1 . 75 million planets considered by the Empire to be advanced and populous enough for full member status . Imperial records further showed five million cataloged examples of sentient species , but it was accepted plainly that there were many more undiscovered species in the galaxy . Behind the scenes . Initially , 5 , 000 , 000 , 000 BBY was the approximate date of the creation of the galaxy , as established by a timeline in " The Essential Guide to Alien Species " ( 2001 ) by Ann Margaret Lewis . " The Essential Atlas " ( 2009 ) by Jason Fry and Daniel Wallace denoted the year 13 , 000 , 000 , 000 BBY as a modern date , and this timeline alteration rectified a potential inconsistency . Before Lewis ' s was released , " " ( 1995 ) by Nigel D . Findley placed 5 , 000 , 000 , 000 BBY as the year around which life first emerged on Goroth Prime — a planet which would have taken quite a long time to form , let alone develop life .