Paolo Del Santo
ABSTRACT
In his brief account of the great comet of 1811, Giuseppe Piazzi (1746–1826), after presenting his observations on the diameter of the nucleus and the determination of the orbital parameters —which constitute the core of the work— offers a series of “thoughts” on comets in general. These reflections, concerning the physico-chemical nature of these bodies and presented as notes set down on paper without any claim to systematic treatment, nonetheless attest to the fact that, at the turn of the new century, cometary science was still far from having developed a shared theoretical framework capable of explaining the constitution of comets and the processes underlying the formation of their immense tails.