Answer:
1) Planetary motion
2) Ellipse
Step-by-step explanation:
Johannes Kepler discovered three laws that mathematically describe the motion of planets around the Sun. According to the first law, every planet moves around the Sun describing elliptical orbits, with the Sun being fixed at one of its focus points. He used the mathematical knowledge of his time to find relationships between the data of the astronomical observations obtained by Tycho Brahe and with them he managed to compose a heliocentric model of the universe. He began working with the traditional model of the cosmos, posing eccentric trajectories and movements in epicycles but found that the observations data placed him outside the scheme that Copernicus had established, which led him to conclude that the planets did not describe a circular orbit around of the Sun. He tried other forms for the orbits and found that the planets describe elliptical orbits, which have the Sun in one of its foci.