In the middle of the nineteenth century, the enterprise of astronomy was transformed by the incorporation of radical new observing techniques and theoretical methods drawn from physics and chemistry. The result was the emergence of astrophysics. A century later, during the 1950s and 1960s, the shift of many physicists to the pursuit of astronomical researches was allied to other crucial changes in terms of the practice, institutional structures, instrumental basis and patterns of patronage of astronomy so that astronomy was fundamentally remade in these years in both North America and in Europe. The migration of physicists to astronomy in these decades constituted therefore the second wave of the remaking of astronomy by physicists. In this paper, I will focus on this migration, what drove it, what were its major consequences, and how it compares with the migration of physicists to other scientific disciplines in the years after World War II.