Trends of K dwarfs

K dwarfs get a lot of attention for habitability-prospects. Also, there are simply a lot of them, not least because none of them have burned out yet like the oldest G dwarfs are starting to. Anyway: David Moore is looking at trends.

The Habitable-Zones (HZ) around red M dwarfs can usually be counted-on to cough up some planets, if tidally locked and irradiated planets. K dwarf HZs, perhaps with nicer HZs, also unfortunately (for observers) have further-out HZs: between 0.26 to 1.04 AU depending on how big the K primary. It takes longer to detect gravitational swings on the star, the massratio gets difficult, and hardly any will transit. So what we've found runs superEarth on-up.

If they don't have a superEarth or Neptunian, what can we speculate about what we don't see - is Moore's aim.

We have a control-set of sorts: TRAPPIST-1, which is M not K. Its worlds are different: mutually-resonant. Pace Moore these, I think, formed in-situ. Moore further claims 20% water-ice. I doubt for the inner ones, even if they were migrates; T-1b is hardly steampunk. But f-g-h could hold it on their dark sides.

For Ks, where not resonant, Moore is finding a lot of planetary migration. 3-6 M supervulcans dominate the ten-day-year zone, which can't be formed in-situ. There's plenty of room in that HZ, but they'd have to have migrated too.

For the migrates I expect waterworlds and carbonworlds. Exception: if the hot innermost planet is a Hot Jupiter. These can scatter protoplanetary rubble such that said rubble then forms in the HZ, citing Martyn (with y) Fogg's PhD-in-progress. That second-generation planet wouldn't own a lot of water.