The System of Saturn

OF CHRISTIAAN HUYGENS

...they may have. In particular, we have often sought to determine whether any companions Huygens uses the term "companions" (Latin: comites) to refer to what we now call natural satellites or moons. are carried around Venus, Mars, or Mercury, yet we have never found any there. Near Jupiter, however, there are four and no more. These are indeed always and easily visible through our telescope, except when Jupiter hides one behind its own disk or within its shadow. From there, as soon as they begin to emerge again, they become conspicuous—indeed, even before they have fully exited, Whitish zones on the disk of Jupiter. as I remember seeing on more than one occasion. Furthermore, the zones or bands original: zonæ seu faſciæ. These are the atmospheric cloud belts of Jupiter, which were a subject of great interest to early telescopists. which have been noticed on Jupiter by some are not always endowed with the same form; these I, and those who have observed with me, have clearly...

A rectangular illustration on a dark, cross-hatched background features three circular planetary disks. At the top left, a disk marked with the astrological symbol for Jupiter (♃) shows four horizontal dark bands. At the top right, another disk also marked with the Jupiter symbol (♃) displays two broad, prominent horizontal dark bands across its center. Below these, a smaller circular disk marked with the symbol for Mars (♂) shows a concentration of fine horizontal lines across its equatorial region, representing early observations of planetary surface or atmospheric features.