Although he was thirty years her senior, Maria Winckelmann fell in love with Kirch and married him in 1690. Kirch gave her further tutoring in astronomy until she became his assistant, then his partner. In 1700 they moved to Berlin where Gottfried became the royal astronomer to Frederick I, the first King of Prussia (and grandfather of Frederick the Great). Frederick promised to build an observatory for him, although it was not completed until after Kirch’s death. The unpaid position was part of the newly founded Royal Prussian Academy of Sciences, which held a monopoly on the sale of calendars. Together the Kirchs produced data for these calendars, as well as for nautical almanacs and astrological charts. From the calendar sales they received a small income. Calendars required a great many astronomical observations since they provided information on the position of the planets, times of sunset and sunset, the phases of the moon, moonrise and moonset, solar and lunar eclipses, etc. Observations were done with small telescopes and quadrants, which measured altitude.
Every night, from their home, Gottfied and Maria would make observations of the heavens. At 2 AM on April 21, 1702 Maria was still watching the skies after her husband had gone to bed. It was then she saw what seemed to be a fuzzy star just above the horizon, something that had not been there the night before. She awakened her husband, who confirmed that she had made the exciting discovery of a new comet. That night two Italian astronomers made the same observation of what would be known as the Comet of 1702 (C/1702 H1). For some reason, Gottfried Kirch initially claimed the discovery for himself, though later would admit the truth, that his wife had seen it first.
Maria Kirch, independent of her husband, published several papers based on her astronomical observations. These dealt with the Aurora Borealis, the conjunction of the sun with Saturn and Venus in 1709, and the conjunction of Saturn and Jupiter in 1712. She made quite a name for herself and was hailed as an example of how the female sex could excel even in scientific fields. Nevertheless, when her husband died in 1710, her attempt to assume his position ran into difficulties. The Royal Prussian Academy of Sciences eventually rejected her, despite her qualifications and the fact that she had been championed by its president, Gottfried von Leibniz, a philosopher and mathematician, famous for inventing calculus (along with Newton). It was obvious Maria had been rejected because of her gender, but also because she held no university degree, (which would have been impossible to obtain since no university at that time admitted women). While progressive men like Leibniz took satisfaction from the achievements of women, there were still many who wished to keep women in their place. The job was given instead to a man of questionable competence.
Despite this setback, Maria Kirch continued to publish works on astronomy. In 1712 a friend and patron of her husband and an amateur astronomer, Baron Frederick von Krosigk, placed her in charge of an observatory he had built with the title of master astronomer. Unfortunately, he died two years later and Maria had to seek employment elsewhere. Briefly, she assisted a mathematics professor in Danzig, but turned down an offer to go to the court of Peter the Great of Russia. She continued to reside mostly in Berlin, where she fulfilled commissions from neighboring states to formulate calendars. She also, quite reluctantly, drew up horoscopes for her friends and clients. Maria, like her husband, had rejected astrology, then still closely linked with astronomy, and, like most astronomers, advocated the not-yet-universally-accepted theory of Copernicus that the earth revolved around the sun and not vice versa. A religious person, Maria argued that the Copernican theory was consistent with Christian teachings.
Gottfied and Maria Kirch had trained their son and three daughters in astronomy and all of them worked in the field. In 1716 son Christfried was able to secure his father’s old position when the man who succeeded Kirch died. He would work at the academy’s observatory, which had been completed in 1711. He was able to bring along his mother and siblings to assist him. Maria, however, ran afoul of the academy members who demanded she make herself scarce when visitors came to the observatory. The presence of a woman doing scientific work and knowing so much about it was apparently an embarrassment to them. Maria was therefore forced to leave and fend for herself. She died of a fever in Berlin on December 29, 1720. Her children continued her work in astronomy.