Kepler law

Kepler’s three laws of planetary motion are:
    •  The law of orbits
    •  The law of areas and
    •  The law of periods

Kepler’s first law
Kepler’s first law, the law of orbits, states that the orbit of a planet is an ellipse with the sun at one of the foci. An ellipse is a closed, curved shape that is defined by two points called foci representing an elongated circle.The closest point on a planet’s orbit from the sun is called perihelion and the farthest point from the sun is called the aphelion. 
Kepler’s second law
Kepler’s second law of planetary motion, also known as the law of areas, states that the line joining the planet to the sun sweeps out equal areas in equal intervals of time as the planet <a href="https://www.nextgurukul.in/wiki/concept/CBSE/VIII/Science/Solar-System.htm" target="_blank"> </a> travels in its orbit.
Kepler’s third law 
Kepler’s third law, the law of periods, defines the relationship between the orbital period of a planet and the average radius of its orbit. The orbital period of a planet, denoted by T, is the time taken by the planet  to make a complete revolution around the sun along its orbit.