The cosmic dance of massive stars

Massive stars might be rare, but their imprints across many astrophysical disciplines are inescapable. They enrich the Universe with heavy elements and ionize their host galaxies. They produce supernovae and gamma-ray bursts. Upon death, they collapse into neutron stars and black holes, which we now observe merging at an ever-increasing rate in the low metallicity, high-redshift Universe via gravitational-wave emission. A major complexity in our understanding of massive stars is that their tendency to interact with companion stars throughout their lives. Such massive-star interactions often lead to their stripping, rejuvenation, or even merging, impacting stellar populations across all masses and galaxies. In my talk, we will journey across the evolutionary path of a prototypical massive binary. I will focus on observed populations of stars that represent distinct evolutionary phases of massive binaries: OB-type binaries, Wolf-Rayet binaries, and black hole binaries. I will present recent advances in our understanding of these populations, including the discovery of a new population of stellar-mass black holes. Finally, I will discuss how future missions and tools will enable us to advance our understanding of these objects and their final supernova explosions at lower metallicities