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MOARdV / qcSystemGenerator

An updated accretion model solar system generator
MIT License
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Gas Giant density gets out of whack #11

Open MOARdV opened 2 days ago

MOARdV commented 2 days ago

Some test runs have gas giant densities approaching 8.5 g/cc - that seems a bit high when rocky planets are around 5.3. Need to figure out why, and add a heuristic to use the alternative radius computation, maybe?

MOARdV commented 1 day ago

Okay ... I think I see why Kothari radius wasn't being used for gas giants in old versions of accrete. Material Zone 1 ends up forming very dense gas giants. So, either I switch back to the other method, or I need to make up new numbers for Z1. I'll go review Fogg 1985 (if I have it) to see if that's where the Z1 gas giant values come from.

MOARdV commented 1 day ago

Even replacing the gas zone 1 value with gas zone 2 leads to occasional failures, but it looks like it's happening mostly with super-Jovian planets.

MOARdV commented 23 hours ago

Here's what I see:

Gas Zone 1 has a high density, which leads to very high density gas giants.

Also, as mass increases, density increases. For instance, at 5.457 AU (Jovian orbit), using Gas Giant material zone 2, Kothari Radius for M(J)=1 is about 71527km (about 2% bigger than Jupiter) with a density of 1.24g/cc. At M(J)=1.25, r=71955km, d=1.52g/cc. At M(J)=1.50, r=72011km, d=1.82g/cc. At M(J)=1.75, r=71852km, d=2.14g/cc.

Using the Solar System's gas/ice giants, with Jupiter and Saturn in Zone 2 and the ice giants in Zone 3, I get errors from Kothari Radius of 1%-9%, with Saturn's radius about 8% high, Uranus's about 9% low.

So, I think the Kothari Radius is an acceptable approach for sub-Jovian-mass worlds,

With the Empirical Density approach, the best it does was Jupiter, with a 6% error (too small). Saturn and Uranus are about 17% off (Saturn 17% small, Uranus 17% large), and Neptune is about 31% off (too large).

I think I'll stick with Kothari Radius after changing Zone 1 to use Zone 2 values for atomic weight and number (to avoid high density gas giants). I'll then see what I can do to manipulate the equations for high-mass giants to avoid collapse - maybe something that incorporates the empirical density approach.

I should also add some random variation to the values (maybe within +/- 10%).