A couple papers are out about how come the systems we see have so many Earths and even super-Earths within and beneath the HZ, and the occasional Hot Jupiter; but few hot Neptunes.
On systems generating super-Earths: Batygin. The western Swiss canton meanwhile offers ideas on the "desert" of Neptunes-chaudes down there.
The Swiss article isn't great. There's talk of the inclination going all wrong when the planet(?s) get too close to the star. Is that just for the few Neptunes we're seeing? It seems like there would have to be interference from Saturn-plus planets further away.
As for the takeaways for would-be science-fiction world-builders (best I see): these articles go to Bayesian analysis of likely K or G class systems where they don't transit. If we don't see planets' shadows, and don't detect their mass; are they there? Answer: there might be an Earth there; these are hard to detect if we don't see the shade. But inasmuch as we detect Hot Jupiters easily, we can probably give up on Hot Neptunes.
I'm interested if super-Earths down the Mercury-Venus levels should hog the material for planets at the HZ level; or, if they don't hog enough, such that HZ is stuck with a superEarth - like to be Venuslike, or an ocean planet.
Another question is if a cluster of biggish planets below, oh, 1.5 AU should enter a Laplacian. How would our planet's tides work if Venus be thrice our mass, and we didn't have a Jupiter above us? Although - sure - here in the HZ this might not matter for tectonics. Maybe we can bargain superVenus to 2:1 (16:8) beneath the nearby 13:8 it is. Inasmuch as a superMars over us would probably squeeze us, Europa-style; I recommend adding a superMercury 2:1, beneath superVenus.
We might have to make that bargain. Venus-as-Neptune 3:2 (12:8) would be... interesting, for us: Earth-Luna as superVenus' own Pluto-Charon. If I am reading the Swiss right we'd be inclined even more than we are, and quite a bit more eccentric - even dipping beneath superVenus' semimajor once a year.
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