Transit of MercuryIn 1631, Pierre Gassendimade the firstobservationof the transit of a planet. Johannes Kepler had predicted a transit of Mercury would occur in 1631. When Gassendi observed the dot of Mercury passing across the face of the Sun, he was surprised - it seemed far too small, according to ancient conceptions of the relative sizes of heavenly objects.With a Galilean telescope he observed the transit by projecting the sun's image on a screen of paper. He recorded this in Mercurius in sole visus (1632; Mercury in the Face of the Sun) as support for the new astronomy of Kepler. His instrument was not strong enough, however, to disclose the occultations and transits of Jupiter's satellites. |
