Stars in Renaissance Science

Stars remained as favored objects of observation during the Renaissance, both from an astronomical and astrological point of view. New, accurate observations of the so-called fixed (stellae fixae) lead to a long re-discussion of many unsettled issues in regard to their nature, such as the understanding of their origin, form, number, light source, twinkling, dimension, position, distance, apparent fixity, and incorruptibility. The revision of traditional conceptions for each of those debated aspects contributed in general to the radical rearrangement and subversion of the Aristotelian-Ptolemaic cosmic model and in particular to the abandonment of the idea of existence of an outer crystal sphere where stars were presumed to dwell and eternally wheel around. Moreover, the discovery of variable stars, the display of unprecedented telescopic observations, and the unexpected appearances of novae in the heavens urged the scientific community between the end of the sixteenth century and the beginning of the seventeenth century to entirely redefine centuries-old notions of unchallenged stellar astronomy. At the same time, the production of more and more precise constellation maps, celestial globes, and star charts helped to reach a better comprehension of the arrangements of stars in the night sky and their relative positions in both the celestial hemispheres, especially for and thanks to intercontinental navigations.