Zacharias Janssen (The Hague, c. 1585 – Amsterdam, before 1632) was a Dutch spectacle maker from Middelburg. Together with his father Hans Janssen he is named as one of the possible inventors of the compound microscope, and possibly of the telescope around 1590.
None of that is settled. The claim rests largely on later witness statements by his son, and Hans Lipperhey, also from Middelburg, was the first to actually file a patent for a telescope, in 1608. Historians still disagree about who built what first. What is certain: around 1600 Middelburg was the centre of gravity of European optics, and shortly after, Galileo Galilei pointed his own version of such a spyglass at Jupiter.
In 2015 the International Astronomical Union gave his name to a real exoplanet: Janssen, better known as 55 Cancri e, a super-Earth some 41 light-years away.
That planet is stop 51 in Aeron and Elias’ donut game, see 2026-08-02 Hoe Aeron en Elias een donut naar de ruimte schoten. They still don’t quite believe our family name is on a planet.