[2] Upon completion of his military service, Antonius moved to Jena, where Georg Wirn was born and lived, and where, in 1571, he enrolled at the university.

At Jena, Limnaeus studied under Jacob Flach (1537–1611), who was a graduate of the University of Wittenberg and had exposure to Philip Melanchthon (1497–1569) and frequented the lectures of Erasmus Reinhold (1511–1553.

[4] In 1597, Limnaeus (along with Galileo, Brahe and Ursus) received a draft copy from Kepler of his first major work, Mysterium Cosmographicum.

On April 24, 1598, Limnaeus wrote to Kepler, expressing his firm belief that heliocentric considerations should not be dismissed from the studies of astronomy by declaring, "Most illustrious Sir, never was I estranged from the most ancient philosophy of the Platonists – nor have I thought, as have several petty philosophers in our time, that it ought to be shunted outside the borders of the territory of the republic of letters."

In light of the disconcerting imprisonment of Giordano Bruno in 1593 (who was executed in 1600), this open expression of both support to young Kepler, and delight in his mathematical astronomical approaches, provided him with some of the earliest, forceful words of encouragement, which he must have welcomed in contrast to the many strong criticisms his work quickly evoked.