[“Observations of Jupiter, Mars and Saturn made at the Roman College”]

"Osservazioni di Giove, Marte e Saturno fatte al Collegio Romano"
Angelo Secchi
Memorie dell’Osservatorio del Collegio Romano, nuova serie, volume II
Roma, Tipografia delle Belle Arti, 1863
Tav. V
300 x 380 mm
Library of INAF-Capodimonte Astronomical Observatory, Naples

Thanks to their high quality optics, Merz telescopes gave excellent results in the observations of planets, obtaining many details. With the Merz telescope of the Roman College, Secchi could then carry out interesting studies on the planets of the solar system. The table reproduced here illustrates some observations of Jupiter, Mars and Saturn. The first two rows at the top show the drawings of Jupiter’s surface, observed between 1856 and 1857, while the two drawings at the bottom left date back to 1863. Secchi noted that the different appearances of the surface of this planet, through the years, induced to think that Jupiter had not a solid state, but a fluid one. The third and fourth rows of drawings reproduce the observations of Mars, also dating from 1863; In the description of this planet, Secchi coined the term “canals” to indicate some rectilinear structures observable on its surface: it is known that this term was then wrongly translated in some English newspapers with the term “channels” instead of ” canals “, alluding to their artificial nature, and thus nursing the debate on the existence of intelligent life on the red Planet. The image in the lower right depicts Saturn, a planet that had aroused the curiosity of Secchi since his earliest studies at the Collegio Romano – he had a brief correspondence with the astronomer William Lassell, an expert observer of the planet, and in the years 1860-1861 studied the disappearance of the ring, a periodic phenomenon due to a perspective effect. It should also be recalled that the first observation of the spectrum of Uranus was made in 1869 (Figure 1) by Secchi. It may be interesting to know that Secchi was a decisive supporter of pluralism, convinced that each star had its own planetary system – something that is now widely demonstrated – and that many of these today so-called “exoplanets” would host life, in various possible stages of its evolution.

Ileana Chinnici, INAF-Osservatorio Astronomico di Palermo