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Keplers Laws
 Keplers laws of planetary motion are a set of three laws describing
the motion of planets around the Sun.
 German mathematician and astronomer Johannes Kepler published
these laws between 1609 and 1619 based on observations made by
his mentor, Danish astronomer Tycho Brahe.
 Although Kepler applied the three laws to planets in the solar system,
they can be extended to planets outside the solar system, asteroids,
and artificial satellites.
 These laws are collectively known as First Law, Second Law, and Third
Law.
Keplers 1st
law
 Statement: All planets orbit around the Sun in a path described by an
ellipse with the Sun at one of its two foci.
 Also known as the Law of Ellipses, Kepler concluded that all solar
system planets have elliptical orbits.
 The Suns center is at one of the foci. When a planet revolves around
the Sun, its distance from the Sun constantly changes.
 The point of the closest approach to the Sun is the perihelion, and the
furthest point is the aphelion.
 Keplers first law is used to study the trajectories of planets, asteroids,
and comets by applying the ellipse equations.
Kepler's laws of orbital motions 1st,2nd,3rd  .pptx
Equation
Equation of an ellipse in a polar coordinate (r, 慮) system is
r = p /1+ 狼 cos 慮
Where,
p : semi-latus rectum
竜 : eccentricity
2nd
Equation.
 Statement: An imaginary line joining a planet and the Sun sweeps
out equal areas in equal time intervals.
 Also known as the Law of Equal Areas, this law implies that the areal
velocity of the revolving planet remains constant. In other words,
planets do not move at a constant speed in their orbits.
 A line segment joining the planet and Sun sweeps out equal parts in
equal time intervals. Hence, the speed of the planet at perihelion is
higher than at aphelion.
 Keplers second law is applied to study the angular speeds at different
points on the trajectory and the magnitude of acceleration
Kepler's laws of orbital motions 1st,2nd,3rd  .pptx
Equation
 The areal velocity is the area swept by the planets orbit divided by
the time taken to sweep it. The following expression gives its value.
dA/dt =L/ 2m
Where ,
dA/dt : Areal velocity
L : Angular momentum of the planet
m : Mass of the planet
Keplers 3rd Law
 Statement: The square of a planets orbital period is directly
proportional to the cube of the orbits semi-major axis.
 Also known as the Law of Harmonies, this law implies that the orbital
period increases rapidly with the orbitssemi-major axis. The ratio of
the squares of the periods to the cubes of the semi-major axes is the
same foreach planet. Keplers third law is used to study the orbital
periods and planets mass.
Kepler's laws of orbital motions 1st,2nd,3rd  .pptx
Equation
 Suppose T is the orbital period and a is the semi-major axis of the
elliptical orbit. Then,
T 2  a3
 T 2 = ka3
 If T is expressed in Earth years and a in astronomical unit (A.U.), then
k = 1.
 The following image summarizes all three laws.
Kepler's laws of orbital motions 1st,2nd,3rd  .pptx

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Kepler's laws of orbital motions 1st,2nd,3rd .pptx

  • 1. Keplers Laws Keplers laws of planetary motion are a set of three laws describing the motion of planets around the Sun. German mathematician and astronomer Johannes Kepler published these laws between 1609 and 1619 based on observations made by his mentor, Danish astronomer Tycho Brahe. Although Kepler applied the three laws to planets in the solar system, they can be extended to planets outside the solar system, asteroids, and artificial satellites. These laws are collectively known as First Law, Second Law, and Third Law.
  • 2. Keplers 1st law Statement: All planets orbit around the Sun in a path described by an ellipse with the Sun at one of its two foci. Also known as the Law of Ellipses, Kepler concluded that all solar system planets have elliptical orbits. The Suns center is at one of the foci. When a planet revolves around the Sun, its distance from the Sun constantly changes. The point of the closest approach to the Sun is the perihelion, and the furthest point is the aphelion. Keplers first law is used to study the trajectories of planets, asteroids, and comets by applying the ellipse equations.
  • 4. Equation Equation of an ellipse in a polar coordinate (r, 慮) system is r = p /1+ 狼 cos 慮 Where, p : semi-latus rectum 竜 : eccentricity
  • 5. 2nd Equation. Statement: An imaginary line joining a planet and the Sun sweeps out equal areas in equal time intervals. Also known as the Law of Equal Areas, this law implies that the areal velocity of the revolving planet remains constant. In other words, planets do not move at a constant speed in their orbits. A line segment joining the planet and Sun sweeps out equal parts in equal time intervals. Hence, the speed of the planet at perihelion is higher than at aphelion. Keplers second law is applied to study the angular speeds at different points on the trajectory and the magnitude of acceleration
  • 7. Equation The areal velocity is the area swept by the planets orbit divided by the time taken to sweep it. The following expression gives its value. dA/dt =L/ 2m Where , dA/dt : Areal velocity L : Angular momentum of the planet m : Mass of the planet
  • 8. Keplers 3rd Law Statement: The square of a planets orbital period is directly proportional to the cube of the orbits semi-major axis. Also known as the Law of Harmonies, this law implies that the orbital period increases rapidly with the orbitssemi-major axis. The ratio of the squares of the periods to the cubes of the semi-major axes is the same foreach planet. Keplers third law is used to study the orbital periods and planets mass.
  • 10. Equation Suppose T is the orbital period and a is the semi-major axis of the elliptical orbit. Then, T 2 a3 T 2 = ka3 If T is expressed in Earth years and a in astronomical unit (A.U.), then k = 1. The following image summarizes all three laws.