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I was looking at Wikipedia's Solar system page, and it says that Sun represents 99.86% of the whole solar system mass. I found that pretty huge.

So i calculated ratio of masses : Earth / (Earth + Moon) and it's about 98.78%.

I did the same with Jupiter : Jupiter / (Jupiter + Io + Europa + Ganymede + Callisto) and it's about 99.97% (I ignored small satellites).

  • Why is it such a high ratio in this 3 examples?
  • Is 1% a regular number for satellites' mass?
  • It is simple gravitation maths ?

I understand that one body has to be much more massive in order to be a planet-satellite system, otherwise it's a double planet system. But I would have thought 90% would be enough.

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No, there is no pattern on 1%. There are cases of double stars and (allegedly) of double planets.

In our Solar System, Charon has a mass of 11.6% of that of Pluto.

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