Maria Cunitz: Astronomy’s Overlooked Genius

 

We all know the role of Johannes Kepler in the revolution of astronomy. The theoretical explanation of the motion of all planets and celestial bodies in space comes from Kepler’s three laws. But it was the astronomer Maria Cunitz who played a pioneering role in making Kepler’s theory more precise and easier to understand. Maria Cunitz was an extraordinary, yet often underestimated, figure of the astronomical revolution and a contemporary of Johannes Kepler.

Astronomy began with an Earth-centred view of the universe. In the second century, Claudius Ptolemy proposed that everything in the universe revolved around the Earth. For nearly fourteen hundred years, Ptolemy’s theory dominated, and all observational research in this field was conducted within the framework of his geocentric model.

But in 1543, after the publication of Nicolaus Copernicus’s theory, Ptolemy’s model was shaken. After many struggles and controversies, Copernicus’s heliocentric astronomy was eventually established. We came to understand that the Earth rotates once on its axis every twenty-four hours—causing day and night—and revolves around the Sun once a year, resulting in the change of seasons. The other planets of the solar system also revolve continuously around the Sun in their respective orbits at definite speeds.

Naturally, the question then arose—how do they revolve? What are the theoretical laws governing the motion of the planets and stars?

Through continuous observation of the planets, the German scientist Johannes Kepler formulated three revolutionary laws concerning the orbits of the planets, their motion within those orbits, and their total periods of revolution. He published the first two laws in 1609 and the third law in 1619.

Kepler’s First Law:
According to the law of elliptical orbits, every planet revolves around the Sun in an elliptical path, with the Sun at the centre. We know that a circle has only one centre, but an ellipse has two centres, called foci. The Sun is located at one of these two foci, and the planets move around it in elliptical paths.

The shorter the distance between the two foci, the more the ellipse resembles a circle. When the distance between the two foci becomes zero, they merge into a single point—this point becomes the centre of a circular path, and the ellipse becomes a perfect circle. At that time, the eccentricity of the ellipse is at its minimum (zero). Conversely, as the distance between the two foci increases, the ellipse becomes more flattened, and its eccentricity increases.

Among the planets, Mercury has the most elongated (flattened) orbit; therefore, it has the greatest eccentricity. As a result, Mercury sometimes comes very close to the Sun and at other times moves far away from it. The point at which a planet is closest to the Sun is called perihelion, and the point at which it is farthest from the Sun is called aphelion. This law of orbits is applied when determining the paths of modern satellites.

Kepler’s Second Law:
According to the law of equal areas, if a straight line is drawn between the Sun and a planet, that line sweeps out equal areas in equal intervals of time as the planet moves along its orbit.

In the diagram, Area-1 = Area-2. Therefore, the time required to move from P1 to P2 is equal to the time required to move from P3 to P4. However, the distance from P1 to P2 is greater than the distance from P3 to P4. So, to travel from P1 to P2, the planet must move faster than it does from P3 to P4.

Thus, a planet’s speed is not the same at all points in its orbit. When a planet comes closer to the Sun, it moves faster; and when it moves farther away from the Sun, it moves more slowly.

Kepler’s Third Law:
According to the law of periods, the closer a planet is to the Sun, the faster it moves in its orbit. The square of a planet’s orbital period (T²) is proportional to the cube of its average distance (R³) from the Sun.

Here it should be remembered that the unit of the orbital period must be years, and the unit of the average distance of a planet from the Sun must be the astronomical unit (AU). The distance from the Earth to the Sun is taken as one astronomical unit. The Earth–Sun distance is about 150 million kilometres. Therefore,

1 AU = 150,000,000 km.

Based on the laws governing the motion of planets and stars, Johannes Kepler published a set of tables to help scientists accurately determine the positions of celestial bodies in space. In honor of Emperor Rudolf II (then King of Hungary and Bohemia), who had patronized astronomical research, Kepler named these tables the Rudolphine Tables.

Although the tables were published in 1627, they were extremely difficult to understand. However, the self-taught astronomer Maria Cunitz recognized their importance and far-reaching usefulness. Over the next twenty-three years, she worked on Kepler’s theories and tables, corrected their errors, and transformed them into a clearer and more user-friendly form.

In 1650, her important book Urania Propitia was published—a work that came to be recognized as the first accurate and reliable book in astronomy.

Maria Cunitz was born around 1610 in Silesia of the Holy Roman Empire, a region that today lies between Poland and the Czech Republic. Her father, Heinrich Cunitz, was a physician. At that time, formal education for women was still prohibited in Europe. However, seeing Maria’s enthusiasm for learning, her father encouraged her to study mathematics, science, philosophy, and various languages.

Gradually, Maria read nearly all the scientific books available at the time—especially those on astronomy. Latin was the formal language of science then; important scientific papers were written in Latin, which she mastered. In addition, to follow scientific research published in other languages, she learned Greek, German, Polish, Italian, and Hebrew. Her fluency in multiple languages, combined with strong mathematical skills, gave her access to the most complex scientific knowledge. She created this opportunity for herself.

Maria Cunitz absorbed everything related to the research of Johannes Kepler. Although Kepler’s Rudolphine Tables were filled with extremely complex mathematical calculations, she had no difficulty understanding them. When the tables were published in 1627, Europe was engulfed in war. From 1618 to 1648, the Thirty Years’ War raged across Europe between Catholics and Protestants, bringing insecurity and instability to everyday life.

Amid this turmoil, Maria continued her studies and research. In 1629, she married Elias von Löwen, a learned physician and amateur astronomer. He became her principal supporter. Since women were barred from formal education and research institutions, Maria received no institutional assistance. Undeterred, she began re-examining all the data in Kepler’s tables from her home.

Maria discovered several errors in Kepler’s logarithmic calculations. Moreover, his methods for determining planetary positions over time were extremely complex. She began correcting these errors and simplifying the methodology. There were inconsistencies in Kepler’s calculations of perihelion and aphelion, which she corrected. She replaced the highly difficult logarithmic procedures with more straightforward arithmetic methods and improved tables. As a result, not only professional astronomers but also amateur astronomers could determine planetary positions more easily. Even the preparation of astronomical almanacs (used by astrologers) became more feasible through her work.

After more than a decade of research, she completed the manuscript of her book by 1645. However, due to the war, it was published five years later. In 1650, she released her book Urania Propitia.

Until then, science had largely remained inaccessible to the general public because it was written in Latin. Maria sought to change this. Following convention, she wrote her book in Latin for scholars, but she also wrote it in German for ordinary readers. Gradually, alongside Latin, German became an important language of science in Europe.

In Maria Cunitz’s time, women were not only barred from formal education but were also denied recognition for their achievements. Her husband, Elias von Löwen, understood this reality. When no publisher agreed to print Urania Propitia, he arranged its publication himself and wrote a preface clearly stating that the entire work was Maria’s own research—because many people at the time assumed that any intellectual work attributed to a woman must actually have been done by a man.

With just one research book, Maria Cunitz achieved lasting recognition in astronomy. For several centuries, astronomers followed her tables and methods. In recognition of her contributions, a minor planet—12624 Mariacunitia—was named after her, and a crater on Mercury also bears her name.

Maria was an ideal seeker of knowledge. She never demanded recognition nor engaged in self-promotion. She devoted her time and dedication entirely to the pursuit of knowledge. She died in 1664.

For many years, her contributions to astronomy were largely forgotten. As barriers to women’s formal education gradually diminished and women’s participation in scientific research increased in the twentieth century, the history of science began to be re-examined. In that reassessment, the overlooked scientists of earlier centuries have regained recognition. Today, we can better appreciate Maria Cunitz’s contribution—she made Kepler’s theories practically usable and accessible.

References

1. Astronomy & Geophysics: The Journal of the Royal Astronomical Society, August 2024, Vol. 65 (4), pp. 4–4.26.
2. Anna Reser and Leila McNeill, Forces of Nature, Frances Lincoln Publishing, London, 2021.
3. Magdolna Hargittai, Meeting the Challenge: Top Women in Science, Oxford University Press, 2023.