I have a Gas Giant with 13x the mass of Jupiter. How many satellites of Earth size and mass can it hold safely in its orbit?

Edit: This gas giant lies smack dab in the middle of its parent star's (Blue Giant) habitable zone.

Edit: I would like to change the star type from Blue Giant to a Yellow Main Sequence Star, due to the issue of the Blue Giant's radiation sanitizing the satellites. The satellites are all intended to be habitable by human standards.

  • $\begingroup$ You need to describe to system where this planet is. I suspect it makes a difference. $\endgroup$
    – L.Dutch
    Commented Jul 1, 2019 at 19:44
  • $\begingroup$ Possibly related: Is it possible to have a non tidally locked moon? as you don't mention: do the moons need to have atmosphere, does planetary eclipsing occur, how old are the satellites relative to planet. As you increase the number of moons, the interactions between the moons get more complicated: tidal heating & tidal locking (i.e. the worlds of Trappist-1) $\endgroup$ Commented Jul 1, 2019 at 20:32
  • $\begingroup$ Thalassan, I thought the orbital-mechanics tag could attract those watching it, I was hoping for an orbital-resonance tag, but it's not been written yet. Please feel free to revert and remove the tag if you wish. $\endgroup$ Commented Jul 1, 2019 at 20:37
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    $\begingroup$ I know I´m kinda late to the party, but blue giants won´t even have planets unless they capture them. They are so hot that they will evaporate their protoplanetary disks before planets can form. $\endgroup$ Commented Jul 1, 2019 at 21:03
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    $\begingroup$ Also of note, at 13 Jupiter masses, your planet is actually a star. Specifically, it is at the lowest bound for brown dwarfs. $\endgroup$ Commented Jul 1, 2019 at 21:16

1 Answer 1


I'm new here so this may be a novice answer but I'm happy to posit an idea. I'' let you take a look at this chart (https://en.wikipedia.org/wiki/Hill_sphere#/media/File:Hill_sphere_of_the_planets.png) from the Wikipedia page on the Hill Sphere around which the moons of planets can orbit.

From what I understand the Hill Sphere of Jupiter is influenced by two main factors: 1) It's distance from the Sun and 2) It's mass. I can figure this by comparing it to all the other celestial bodies shown. The Inner Planets have smaller Hill Spheres than the Outer Planets due to being closer to the Sun meanwhile whereas Jupiter clearly having a larger HS than the Earth or Mars owes to its greater size as well as distance, the fact that Neptune has the largest HS proves that distance from the parent star can influence HS size to greater degree.

Now for what this means for your planet. You've changed the star I see. If it's sun like then that makes it a little easier. You need to take into account the effect of tidal heating of you're moons around such a large planet which might actually require you push it out further than Earth. The type of planet or planetary system can determine where is most habitable too. This increases the Hill Sphere size.

I think someone more mathematical than me could work out the math from here but I provided a base to work off.


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