How to calculate the mass of the sun?

Newton’s form of Kepler’s 3rd law describes the orbit of a planet around the Sun. From this law we can calculate the mass of the sun.

p2=4π2/GM a3

P is the orbital period;
G is the gravitation constant;
M is the mass of the Sun;
a is the orbit semi major axis distance.

Rearranging the equation gives:

M=4π2a3/Gp2

Now for planet Earth: a = 1.496⋅1011 m

p = 3.154⋅107s

G=6.67408⋅10−11m3Kg−1s−2

Substitute all the values to the equation and thus gives the mass of the sun M=1.99⋅1030Kg

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