The engraving is among the first visual and interpretative accounts of the auroral phenomenon observed from Italy. Sguario attempts to explain the aurora through the principles of Newtonian mechanics, reflecting the spirit of the Enlightenment, which aimed to reconcile wonder and rationality. Although rare in southern latitudes, the aurora borealis has always aroused wonder, awe, and curiosity, fueling scientific, artistic, and literary interest. In Naples, observations of these events are documented from the 16th to the 20th century, revealing the fascination these celestial lights exerted on society and the scientific community.
Auroras, or polar lights, are caused by the interaction between charged particles emitted by the Sun and the gases in Earth's atmosphere. During periods of intense solar activity, particularly at the peaks of the eleven-year solar cycle, coronal mass ejections can project plasma toward Earth. If directed toward our planet, these particles penetrate the magnetic field and head toward the poles, where they excite oxygen and nitrogen atoms in the upper atmosphere (between 80 and 500 km), generating beams of colored light. To be visible from Naples, solar storms must be particularly intense, capable of illuminating a very extensive atmospheric layer. From here, looking north, it is possible to see the highest part of the aurora, often characterized by red flashes due to the de-excitation of oxygen at high altitudes.
Among the eighteenth-century accounts, that of Francesco Serao, professor of anatomy and medicine and secretary of the Academy of Sciences founded by Celestino Galiani, stands out. He precisely described the aurora of December 16, 1737, in a letter sent to Galiani. A second sighting, on March 29, 1739, was recorded by the Royal Pages of Naples, where Francesco Maria Pertusio directed a small observatory frequented by Felice Sabatelli and his students. The first scientific explanations were consolidated in 1741, when Anders Celsius and Olof Hiorter associated variations in the magnetic needle with the influence of the auroras, introducing the concept of a geomagnetic storm. Jean-Jacques Dortous de Mairan, in his Treatise on the Physics and History of the Northern Lights (1733 and 1754), confirmed the polar nature of the phenomenon, attributing it, however, to atmospheric vapors, ruling out electrical or magnetic causes. In 1778, Benjamin Franklin hypothesized that auroras were generated by electrical charges concentrated in the polar regions, intensified by snow and humidity. These theories, born from rare and surprising observations such as those in Naples, demonstrate how celestial phenomena have stimulated widespread and interdisciplinary scientific research.

___Clementina Sasso