Learning the Physical Science of Binary Stars

Johannes Kepler (1571-1630)   For more information on Kepler's Laws: More on Kepler's Laws from Central Valley Christian School Astr 1010 Lab on Planetary Motion

Keplers Laws of Planetary Motion 1st Law: Planets orbit the Sun in an elliptical Path with the Sun at one focus. 2nd Law: An imaginary line connecting the Sun to any planet sweeps out equal areas ot the ellipse in equal intervals of time. 3rd Law: The square of a planet's orbital period is propotional to the cube of its semi-major axis. Mathmatically this can be stated as P2 = a3 where P = orbital period in years, and a = semi-major axis in AUs. (AU stands for astronomical uiit. One AU is the average Earth-Sun distance.)

Sir Isaac Newton (1642-1727)

Newton' Laws of Motion and Law of Gravitation Laws of Motion   1st Law: Every body continues in a state of rest or in a state of uniform motion in a straight line unless acted upon by an outside force.   2nd Law: When a force, F, acts on a body with mass, m, it produces an acceleration, a, equal to the force divided by the mass. Mathematically this can be written as a = F/m or F = ma.  NOTE: The, a, in this eqaution stands for acceleration and should not be confused with the semi-major axis of an ellipse which is also represented by an, a. This is an unfortunate overlap of variable nanes, which is historic in nature and we have to deal with it. 3rd Law: For every action there is an equal and opposie reaction.   Law of Gravitation Every particle of matter in the universe attracts every other particle in the universe as if a force act on them that is directly propotional to the product or their individual masses, m1 & m2, and inversely proportional to the square of the distance between them, R. Mathematically this can be written as F = G(m1m2)/R2, where G is the gavitational constast of proportionality and is equal to 6.67x10-11 newton meter2/kg2.

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