Habitability of my world

Question

For a big narrative project of mine I and my team developed an habitable moon that revolves around a gas giant in a star system with an F-star. I wanted to know what you think about it and if you think it would make sense to have the moon habitable.

I'll start with the star. It would be an F-star 1.3 times the mass of the sun and of an age of 2.5 billion years.

Next there would be the gas giant. The gas giant would be 3 times the mass of jupiter and orbit at a distance of 2 AUs from the star being it's 5th overall planet. It also has an axial tilt of 20 degrees.

Finally the moon. The moon is about 0.7 times the mass of the earth and orbits at a distance that allows for a 36 hours long orbital period and thus day since it's tidally locked, it has an orbital inclination to the giant's orbital plane of 10 degrees, which combined with the gas giant's axial tilt makes for a 30 degrees inclination to the star's plane making seasons possible and more 'extreme' than earth's. It would be one of the many moons the gas giant would have thanks to it's mass, which I figured would be about 10 or so plus a hundred of minor ones. The moon itself would have a thick breathable atmosphere rich in CO2 and screening gases such as ozone and would feature a magnetic field capable of shielding the moon from the gas giant's and the star's radiation, thanks to the higher percentage of iron in it's core and mantle and thanks to the graviational interference of the other moons and the gas giant.

Will my moon be habitable?

Answer 1

Hi there and welcome to Worldbuilding! I hope this leads you in a good direction and doesn't sound too critical - your moon seems like quite a fun place to go. And these are all napkin calculations, so take them with a 1 AU-wide grain of salt!

According to this Wikipedia article, the star's luminosity 2.86 times our sun's (=1.3^4), and according to this one, the habitable zone would be centered at 2.26 AU (=1.34 x square root of 2.86). So sitting at 2 AU is pretty similar to the earth, which is 0.34 AU inside our goldilocks center. But the huge gas giant would probably cause quite a bit of tidal heating on the moon, so you might want to move it somewhat farther from the star, perhaps closer to 2.26 AU or a little farther. That would probably mean dimmer sunlight than we're used to on earth.

As some have commented, the age is rather young for life to process that comfy atmosphere, but maybe factor it into your story - e.g. life was seeded or cultivated there, high adaptation pressure, etc.

The planet's large magnetic field is a double-edged sword. It will protect the moon from a ton of cosmic and solar radiation, but it will accelerate any sources of free particulate to create its own dangerous radiation. Jupiter accelerates Io's sulphur volcanism output into a belt of very destructive ionizing radiation. Basically the neighborhood must be very tidy. 10 major moon neighbors are each sources of radiation ammo, so maybe fewer or very far orbits. An easily pickpocketed thick atmosphere on a moon smaller than earth is more of a threat than a blessing. Instead, maybe protect it from the F-star's heavy UV radiation by moving farther out in the goldilocks zone and lean into tidal heating for warmth.

At 2 AU and 3 Jupiter masses, the planet is quite close to squeeze 4 planets next to a star even bigger than the sun. Its gravity would probably have an enormous affect on such close planets; note that Jupiter is at 5.2 AU and the closest thing to it is a crumbly asteroid belt centered at 2.7 AU. This is just guesswork, but I'd say move the planets beyond the gas giant. Maybe 1 interior planet and 1 belt? But who knows? Put a lampshade on it and it could work.

That orbital inclination is nuts. Most solar system planets are within about 2 degrees of the invariable plane, which is in fact set by the mass of our gas giants. See this table. Basically, where your gas giant goes, so do the other planets. So you're gonna need something quite significantly bigger than your gas giant elsewhere in the system to set the baseline differently, and some crazy impact or stellar flyby story to explain how a 3-Jupiter gas giant in the inner planets is more out of whack than Pluto.

The 36-hour orbital period might be cutting it very close to the gas giant. Just comparing Jupiter's major moons puts it relatively closer than Io, the closest, which is ravaged and torn by its proximity to Jupiter. But your moon is bigger, and it would take more math than I have time for to be sure.

Cheers!