Hycea

New term, h/t Glenn Reynolds: the Hycean Planet. This is a water-world with a hydrogen-dominant atmosphere. Almost a Neptune: not supercritical.

I take it that when oxygen is given off, oxygen not being very hydrosoluble; it reacts with the atmosphere and just rains back onto the ocean.

Cambridge University is looking between 35-150 light years away because that's where they've found the transits. Closer in, we're not lucky enough to see a Hycean transit. Further out I suppose it's just too far to see much.

As far as life is concerned I am... skeptical, at least of our ability to find it. Just as our planet (until recently) has been busily sequestering its carbon, a water world with an alga / animal cycle would be dumping its carbon onto its own (VERY deep) seabed that much more efficiently. There might be life on that seabed but, er, Not As We Know It. And it's never coming up to the surface. Because there's nothing to eat up there.

And there's no sunlight down on the bottom. Honestly it's all going to look a lot like Europa and we're better off looking there.

AS WE KNOW IT 5:25 PM MST: If the world-ocean is shallow enough, at least in places, we can muse about some carbonbased photosynthetic plants that extend toward the sunlight. Symbiosis will be key. Also where the planet is tidally-locked and the sun doesn't flare too bad, will be a nightside icecap; some lichen might cling to that cap's edge. Yeah, I know; we're reaching.