Would my gas giant have rings?

Question

The gas giant in question is about 3 times the mass of jupiter with a density of 3.58 grams per cubic centimeter. It formed naturally beyond the system's forstline and then migrated into the habitable zone at about 2 to 2.26 AUs from it's parent F-star 1.31 times more massive than the sun, acquiring a couple of additional satellites around the end of the migration on rather distant orbits (10 to 20 planetary radii).

First of all, can a gas giant with that mass and density have rings? How thick could they be?

Would it still retain the rings after migration?

How much would the rings be impacted by the increased solar energy? How thinner would they get if they lost most of the ice?

Answer 1

It may or may not have rings

Rings are generally caused by an orbiting body breaking apart, either due to gravitational forces (e.i. the body gets to close to the parent planet, and is torn apart by tidal forces), or due to an orbital collision.

Non of the factors you have specified make it impossible for rings to have formed. Rings are much more caused by what is orbiting the planet, rather than the parameters of the planet itself.

However the stability of the rings, and how long they are likely to survive are determined by many other parameters. You have mentioned solar distance, and it is likely that if the (hypothetical) body which broke apart to create the (hypothetical) rings was predominantly icy, then much of the ice may have sublimated away, leaving thin rings. If the originating body was rocky or metallic, then a well developed ring system may still persist for long timescales.

Another key factor in the stability of the rings is the presence of other satellites with compatible orbital resonances. To simplify, orbital bodies will tend to pull and push each other over eons until they occupy nice ratios of orbital period (e.g. with Jupiter, Io orbits roughly every 42 hours, Europa orbits about every 84 hours, and Ganymede orbits about every 168, creating a nice 1:2:4 ratio). The structure of rings would be expected to fit with orbital resonances of the planet's moons (for example, Saturn's rings have a large gap known as the Cassini Division, which matches a 2:1 resonance with Mimas). If new satellites were gained after the formation of the rings, they could disrupt them, and eventually lead to an altered ring structure, or even a dissolution of the rings. This would all depend on a great many factors, so there is no way to know.

Much of this is conjecture, as we are ultimately only able to observed the dynamics of ringed planets in our own solar system. It is possible that further effects (perhaps things like the Yarkovsky effect?) may be more important for gas giants which orbit close to their parent star. Given that we do not yet have the ability to image rings around exo-planets, I do not believe astronomers can currently say for certain if all aspects of ring dynamics are fully known.

Answer 2

Yes. And they are the reason why all the moons are habitable.

Your gas giant and its 20 moons are in the "habitable zone". Any body with a decent atmosphere and oceans (for the water vapor greenhouse contribution) will be habitable. The slow action of UV light has even liberated oxygen for a breathable atmosphere. But there was one catch, namely that there was a low-density moon made of mostly water ice that could not hold a thick atmosphere, and some other rocky moons that were devoid of water and atmosphere.

So what happened? Well, the water on the water moon escaped. It went flying off into space. But when I say flying off into space, I don't mean those water molecules could escape Super Jupiter; that's just impossible. And they had high angular momentum when they left the atmosphere, so they rarely fell into it either. So ... they drift, as isolated gas particles, round and round, until they precipitate as ice (because they are not under a warming atmosphere) or else bump into some other moon.

The rings are a massive reservoir of water, which has since distributed itself almost equitably onto all the little moons. None of them is quite big enough to hold an atmosphere, but that atmosphere keeps coming back as fast as it is lost.