I would like to draw the attention of historians of astronomy to some unpublished representations of historical comets in Renaissance paintings, frescoes and reliefs from central Italy, which testify to a diffuse interest in the celestial novelties of the second half of the 16th century, even on the part of artists. The approach to such representations is mostly naturalistic and influenced by scientific debates on the eve of the Scientific Revolution, as has already been noted in subsequent artistic depictions (Olson & Pasachoff, 1998), but a persistent astrological component related to prophecy and astral divination is still present.

The first object, suggested by a careful study of the portrait of an astrologer in Prospero Fontana's 1565 painting in the Galleria Spada in Rome and by the analysis of the celestial globe in the foreground, is probably the Halley in its 1531 passage. This particularly tricky and elusive representation was noted by the art historian Aby Warburg (1911), but never studied in depth. I will show that the celestial body, which is closely linked to the enigmatic representation of a comet in a late portrait of the Sienese cosmographer Alessandro Piccolomini from the beginning of the 17th century preserved in Pienza, was captured at the very beginning of its visible trajectory in the sky, in a sense truly "discovered" by the astronomer, proudly displaying its presence on the globe.

Another interesting portrait of a famous comet - that of 1577, studied by Tycho Brahe and many other astronomers of the time - can be found in the Palazzo del Commendatore of the Hospital Santo Spirito in Sassia, also in Rome. It is a simple sketch in the Mannerist decoration of the central Salone, executed by an unknown painter in the very year of its appearance, when the local confraternity in charge of the great hospital was led by Teseo Aldrovandi, brother of the Bolognese naturalist Ulisse. The presence of the moon in the small fresco on a black background allows us to date the comet portrait approximately.

The last comet is on the eastern façade of the Villa Medici, another magnificent Roman building, created by Bartolomeo Ammannati for Cardinal Ferdinando de Medici between 1576 and 1585. The object is well disguised as an eight-pointed star above the famous relief of the Judgement of Paris from an ancient sarcophagus, copied by Raphael and cited by Manet. The object is depicted next to a large fish on a band of zodiacal constellations: a complex analysis suggests that it could be an allusion to the comet of October 1585 in the constellation of Cetus, which, according to the astrological theory of the great conjunction of Jupiter and Saturn, heralded a new golden age for the Medici and the personal triumph of Ferdinando, who ascended the throne of the Grand Duchy of Tuscany two years later. Some time earlier, from the gardens of the same villa, the cosmographer Antonio Santucci delle Pomarance had observed and studied another bright comet: that of March 1582.