So I'm working on a fictional system that is based on several habitable moons orbiting a Gas Giant. The Specifics are as follows:

  • Mass of the central Star (Currently): 3 Solar Masses

  • Mass of the Gas Giant: 11 Jupiter Masses

  • Semi Major Axis of the Host Planet: 7.75 AU

  • Mass of the Moons from inside to outside in Earth-Masses:

  • 3 Moons posess 0.6

  • 3 Moons posess 0.8

  • and the outermost 2 have 1.5 and 2 Earth Masses respectively

So my simulation is stable but, according to the answers to my previous post, not habitable. The reason seems to be that the star in my Simulation is too hot and massive and thus will burn away the moon's atmospheres. This being the case due to its hazardous UV-Radiation. I'm looking into 2 ways to fix it.

1. Change the Gas-Giant into a Brown Dwarf/failed Star and the Star type from a very luminous Type F/A star to a sun like G-Type or a smaller F-Type Star.


  • Since the Brown Dwarf has a superior Mass compared to a gas giant, it's hill sphere is bigger and thus I can fit in the number of moons I desire.
  • Less UV-Radiation from the central star and thus an actual chance of life.
  • Sufficient Live Span of the Star.


  • The Brown Dwarf emits x-Ray radiation and causes even bigger tidal heating than the gas giant already seems to do (according to simulations in Space Engine and Universe Sandbox)
  • In General, the hill sphere of the Gas-Giant/Brown Dwarf is getting to small if i calculated it correctly.

2. Making up my own Star-Type

I could also resort to creating my own fictional/not yet discovered star class which would give me the total freedom to say stuff like "This star is super massive, super inflated, and more luminous but produces mainly infrared and only a small amount of UV-Radiation. Oh and it exists long enough in order for life to evolve because i say so"

Im posting the inner and the outer area of the lunar System below:

Inner System

Outer System

My Question is: Which option is best if I want both the best chances of the moons (except the innermost one) being habitable on the surface and being the most believable scenario for an average, can i say "not too nerdy" audience? For the "fictional Star Type" i would open up a new question if needed.

  • 4
    $\begingroup$ Take the "invent my own star type" option. I'm serious. That's the quintessence of worldbuilding. Sometimes we're too stuck on the desire to be so "realistic" that we can't look beyond what we know to be possible into the realm of what we think is impossible to discover a whole new boundary we never knew existed. All that begins with a good imagination. I love it. $\endgroup$
    – JBH
    Commented Apr 22 at 17:27
  • $\begingroup$ Thank you for the Answer. So my follow up question would be: How does the climate differ on a specific moon from the climate on earth, assuming its day/night cycle is 39 Hours compared to the 24 hours on earth? Maybe its best to create a new question for that $\endgroup$ Commented Apr 22 at 17:50
  • $\begingroup$ That would definitely require a new question. It's also a very broad question and climate questions are the most difficult to answer because there are so many variables. You need to give us all the stats about the star, the moons and their parent planet, as well as a map of the target moon. With that we can give you general guidelines - climate is that difficult. $\endgroup$
    – JBH
    Commented Apr 23 at 3:32


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