VOX LUX begins in 1999 when teenage sisters Celeste (Raffey Cassidy) and Eleanor (Stacy Martin) survive a seismic, violent tragedy. The sisters compose and perform a song about their experience, making something lovely and cathartic out of catastrophe — while also catapulting Celeste to stardom. By 2017, the now 31-year-old Celeste (Natalie Portman) is mother to a teenage daugh…