The Mass of an Extra-solar Planet calculator computes the mass of a planet based on the mass of the star (M), the distance to the star (R) and the distance to the planet (r).
INSTRUCTIONS: Choose the preferred units and enter the following:
- (M) This is the mass of the star.
- (R) This is the orbital radius of the planet.
- (r) This is the orbital radius of the star about the center of mass.
Planet Mass (m): The calculator returns the mass of the planet in Jupiter_Mass units (multiples of the mass of Jupiter). However, this can be automatically converted to other mass units (e.g. Earth_Mass or kilograms) via the pull-down menu.
The Math / Science
If you know the mass of a star, and the orbital radius of the star and the planet, you can compute the mass of the planet using the fact that the center of mass obeys the relation: m•R = M•r. The formula for the mass of a planet is:
m = (M•r)/ R
where:
- m = mass of the planet
- M = mass of the star
- r = orbital radius radius of the star
- R = orbital radius of the planet
Example:
Consider Jupiter in our own solar system:
- (M) The mass of our star (the Sun) is 1.0 Solar_Mass
- (R) This orbital radius of Jupiter is 5.2 ua
- (r) The orbital radius of our Sun around the solar system's center of mass is 0.005 ua
If you enter the above, the calculator returns an exoplanet mass of approximately 1 Jupiter Mass which fits the model and describes our solar system.
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