Title: Cosmos
Content:  Astronomer and mathematician Nicolaus Copernicus was appointed by the Catholic Church as an official, as his uncle was a bishop in the church. He used his income to further his studies, eventually studying at the University of Bologna in Italy. Copernicus began doubting the knowledge of natural philosophers and their beliefs, claiming that geometrical astronomy instead would result in the true reality of the cosmos. His manuscript, De revolutionibus, pioneered ideas that would change the course of how both the cosmos and astrology were viewed. Most notably, Copernicus claimed that the sun was the stationary center of the universe. His work also included calculations on the motions of the moon, and the motions in latitude and longitude of the planets, all which orbit the sun. Copernicus' work was not immediately published as it disagreed with Biblical teachings, and he feared his work would be rejected by Catholic officials.
Title: Nicolaus Copernicus
Content:  1511 fulfilled the duties of chancellor and visitor of the chapter's estates. His administrative and economic duties did not distract Copernicus, in 1512–15, from intensive observational activity. The results of his observations of Mars and Saturn in this period, and especially a series of four observations of the Sun made in 1515, led to the discovery of the variability of Earth's eccentricity and of the movement of the solar apogee in relation to the fixed stars, which in 1515–19 prompted his first revisions of certain assumptions of his system. Some of the observations that he made in this period may have had a 
Title: Nicolaus Copernicus
Content:  Nicolaus Copernicus (Mikołaj Kopernik;, modern: Nikolaus Kopernikus; 19 February 1473 – 24 May 1543) was a Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its center. In all likelihood, Copernicus developed his model independently of Aristarchus of Samos, an ancient Greek astronomer who had formulated such a model some eighteen centuries earlier. The publication of Copernicus' model in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), just before his death in 1543, was a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution. Copernicus was born and died in Royal Prussia, a region that had been part of the Kingdom of Poland since 1466. A polyglot and polymath, he obtained a doctorate in canon law and was a mathematician, astronomer, physician, classics scholar, translator, governor, diplomat, and economist. In 1517 he derived a quantity theory of money—a key concept in economics—and in 1519 he formulated an economic principle that later came to be called Gresham's law.
Title: Copernican heliocentrism
Content: Kepler in 1609 introduced the idea in his Astronomia nova that the orbits of the planets were elliptical rather than circular, while retaining the heliocentric concept. ; Using the newly invented telescope, in 1610 Galileo discovered the four large moons of Jupiter (evidence that the Solar System contained bodies that did not orbit Earth), the phases of Venus (the first observational evidence not properly explained by the Ptolemaic theory) and the rotation of the Sun about a fixed axis as indicated by the apparent annual variation in the motion of sunspots; ; With a telescope, Giovanni Zupi saw the phases of Mercury in 1639; ; Isaac Newton in 1687 proposed universal gravity and the inverse-square law of gravitational attraction to explain Kepler's elliptical planetary orbits. The Copernican Revolution, a paradigm shift from the Ptolemaic model of the heavens, 
Title: Historical models of the Solar System
Content:  Nicholas Copernicus, in reflecting about Ptolemy and Aristoles interpretations of the Solar System, believed that all the orbits of the planets and Moon must be a perfect uniform circular motion despite the observations showing the complex retrograde motion. During the 16th century, Nicholas Copernicus introduced a new model which was consistent with the observations and allowed for perfect circular motion. This is known as the Heliocentric model where the Sun is placed at the centre of the Solar System and the Earth is, like all the other planets, orbiting it. The heliocentric model also resolved the varying brightness of planets problem. Copernicus also supported the spherical Earth theory with the idea that nature prefers spherical limits which are seen in the Moon, the Sun, and also the orbits of planets. Copernicus believed that the universe had a limit, a spherical limit. Copernicus contributed further to practical Astronomy by producing advanced techniques of observations and measurements and providing instructional procedure. 
Title: Copernican Revolution
Content:  telescope with enough magnification to allow him to study Venus and discover that it has phases like a moon. The discovery of the phases of Venus was one of the more influential reasons for the transition from geocentrism to heliocentrism. Sir Isaac Newton's Philosophiæ Naturalis Principia Mathematica concluded the Copernican Revolution. The development of his laws of planetary motion and universal gravitation explained the presumed motion related to the heavens by asserting a gravitational force of attraction between two objects. In 1596, Kepler published his first book, the Mysterium Cosmographicum, which was the second (after Thomas Digges, in 1576) to endorse Copernican cosmology by an astronomer since 1540. The book described his model that used 
Title: Nicolaus Copernicus
Content:  to Italy in 1503) than to studying the humanities—probably attending lectures by Filippo Beroaldo, Antonio Urceo, called Codro, Giovanni Garzoni, and Alessandro Achillini—and to studying astronomy. He met the famous astronomer Domenico Maria Novara da Ferrara and became his disciple and assistant. Copernicus was developing new ideas inspired by reading the "Epitome of the Almagest" (Epitome in Almagestum Ptolemei) by George von Peuerbach and Johannes Regiomontanus (Venice, 1496). He verified its observations about certain peculiarities in Ptolemy's theory of the Moon's motion, by conducting on 9 March 1497 at Bologna a memorable observation of the occultation of Aldebaran, the brightest star in the Taurus constellation, by 
Title: Astronomy
Content:  During the Renaissance, Nicolaus Copernicus proposed a heliocentric model of the solar system. His work was defended by Galileo Galilei and expanded upon by Johannes Kepler. Kepler was the first to devise a system that correctly described the details of the motion of the planets around the Sun. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was Isaac Newton, with his invention of celestial dynamics and his law of gravitation, who finally explained the motions of the planets. Newton also developed the reflecting telescope. Improvements in the size and quality of the telescope led to further discoveries. The 
Title: Nicolaus Copernicus
Content:   Georg Joachim Rheticus could have been Copernicus's successor, but did not rise to the occasion. Erasmus Reinhold could have been his successor, but died prematurely. The first of the great successors was Tycho Brahe (though he did not think the Earth orbited the Sun), followed by Johannes Kepler, who had collaborated with Tycho in Prague and benefited from Tycho's decades' worth of detailed observational data. Despite the near universal acceptance later of the heliocentric idea (though not the epicycles or the circular orbits), Copernicus's theory was originally slow to catch on. Scholars hold that sixty years after the publication of The Revolutions there were only around 15 astronomers espousing Copernicanism in all of Europe: "Thomas Digges and Thomas Harriot in England; Giordano Bruno and Galileo Galilei in Italy; Diego Zuniga in 
Title: Science in the Renaissance
Content:  time. The last major event in Renaissance astronomy is the work of Nicolaus Copernicus (1473–1543). He was among the first generation of astronomers to be trained with the Theoricae novae and the Epitome. Shortly before 1514 he began to revive Aristarchus's idea that the Earth revolves around the Sun. He spent the rest of his life attempting a mathematical proof of heliocentrism. When De revolutionibus orbium coelestium was finally published in 1543, Copernicus was on his deathbed. A comparison of his work with the Almagest shows that Copernicus was in many ways a Renaissance scientist rather than a revolutionary, because he followed Ptolemy's methods and even his order of presentation. Not until the works of Johannes Kepler (1571–1630) and Galileo Galilei (1564–1642) was Ptolemy's manner of doing astronomy superseded.

Question: what did nicholas copernicus discover?
Answer: He discovered that other ancient Greeks had suggested the idea of a heliocentric universe, and this seemed better seemed even though it still needed complex mathematical calculations to predict planetary movement.