 Once a courtier, Galileo entered into several debates on scientific topics. In 1612, he published a Discourse on Floating Bodies, and in 1613, Letters on Sunspots, where he first openly expressed support for Copernican heliocentrism. In 1613–14, Galileo entered into discussions of Copernicanism through his student Benedetto Castelli, and wrote a Letter to Castelli defending the doctrine from theological objections. Meanwhile, it had become known that Copernicanism was under scrutiny by Church authorities. Galileo lectured and lobbied against its condemnation, expanding his Letter to Castelli into the widely circulated Letter to the Grand Duchess Christina in 1615 and travelling to Rome late that year. Nevertheless, in March 1616, Copernicus’s On the Revolutions of the Heavenly Orbs was suspended (i.e., temporarily censored), pending correction, by the Congregation of the Index of Prohibited Books. Galileo himself was called to an audience with Cardinal Robert Bellarmine, a leading theologian and member of the Roman Inquisition, who admonished him not to teach or defend Copernican theory. (The details of this episode are far from straightforward, and remain disputed even today. See Shea and Artigas 2003; Fantoli 2005.)