The Vera C. Rubin Observatory LSST will open a new era for optical astronomy by imaging the Southern Sky at unprecedented depths, detecting millions of time-changing astrophysical objects each night over a decade. I will introduce the project I lead, Fink. Fink’s goal is to discover the most promising astrophysical transients in large surveys and has privileged access to the mega facility Rubin Observatory. I will present our latest research on extreme transients with Fink.
I will also showcase tantalizing new evidence that Dark Energy may not be constant with time. I will present my work on supernovae and machine learning and explain how it contributed to the tightest cosmological constraints to date with the Dark Energy Survey. I will conclude by discussing how Rubin will enable us to shed light on the diversity of transients and, for the first time, to find out whether Dark Energy is a constant or evolving with time.