In November 1572, a brilliant new star appeared in the constellation Cassiopeia, shining so brightly that it was visible during the day. Danish astronomer Tycho Brahe carefully documented this celestial phenomenon, and the supernova remnant that bears his name has been studied intensively ever since. Now, a new analysis of recent observations suggests that Tycho’s supernova had a more dramatic origin story than previously thought: it exploded not in empty space, but inside the ghostly remains of a planetary nebula.