In the last edition of his Commentarius in sphaeram Ioannis de Sacrobosco, published in 1611, Christoph Clavius urged astronomers to work out an astronomical solution that integrated the ground-breaking Galilean novelties of 1610. As the Collegio Romano mathematics professor stated, « since this is so, astronomers ought to see how the celestial orbs may be arranged in order to save the phenomena ». What was the real meaning of Clavius’s plea? This article answers this question by analysing the astronomical work of the Jesuit Giovanni Paolo Lembo. In addition to being an accomplished telescope maker and astronomical observer, having played a crucial role in the telescopic observations carried out at the Collegio Romano between 1610 and 1611, Lembo was one of the closest collaborators of Clavius and an advocate of his astronomical ideas. Shortly after Clavius passed away, Lembo set forth a geo-heliocentric system of Capellan inspiration that came to terms with the Galilean novelties (and particularly with the phases of Venus and Mercury) while simultaneously retaining intact the foundations of Clavius’s astronomical and cosmological ideas. Were Lembo’s interpretation of Clavius’s enigmatic plea correct, the astronomical system he put forward might well encapsulate the solution that Clavius had in mind in the aftermath of observations of the Galilean novelties.

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Giovanni Paolo Lembo,Christoph Clavius,Galileo Galilei,Galilean novelties,Phases of Venus and Mercury,Collegio Romano,Jesuits,Martianus Capella

• History and Archeology - Humanities