explain all Kepler laws .

In astronomy, Kepler’s laws of planetary motion are three scientific laws describing the motion of planets around the sun.

• Kepler first law – The law of orbits: According to Kepler’s first law,” All the planets revolve around the sun in elliptical orbits having the sun at one of the foci”. The point at which the planet is close to the sun is known as perihelion and the point at which the planet is farther from the sun is known as aphelion.
• Kepler’s second law – The law of equal areas::  ” The radius vector drawn from the sun to the planet sweeps out equal areas in equal intervals of time”
  As the orbit is not circular, the planet’s kinetic energy is not constant in its path. It has more kinetic energy near perihelion and less kinetic energy near aphelion implies more speed at perihelion and less speed (v_min) at aphelion. If r is the distance of planet from sun, at perihelion (r_min) and at aphelion (r_max), then,
  r_min + r_max = 2a × (length of major axis of an ellipse) . . . . . . . (1)
• Kepler’s third law – The law of periods: 

  According to Kepler’s law of periods,” The square of the time period of revolution of a planet around the sun in an elliptical orbit is directly proportional to the cube of its semi-major axis”.

  T² ∝ a³