Exoplanet Discoveries and Updates

[AstroChara]

Astronomer, you seem like the right person to ask this. Water worlds, or giant liquid worlds like described here are news to me. Are these a relatively new idea or have they been around? Has the OA delved into these much?

I assume they're not exactly new. The idea is probably around for quite a long while, maybe at least a decade, but only after Kepler starts revealing the planetary demographics do we learn that many planets are super-Earths and sub-Neptunes. We don't have those in OA, so we don't see many of them in OA as a result. More at here for figuring out what these planets may be like, and here for planetary abundances.

[Drashner1]

Er. Actually we have:

a) An entire page devoted to super-terrestrial worlds that dates back to 2011 - LINK

b) Panthalassa (LINK), which is a pretty wet place (article written in 2008) and IIRC is also an example of the PanThalassic Type world - LINK (article written in 2008).

Is there something distinctly different about super-Earths and water worlds that clearly makes them not examples of what is described above? At the least, I think it's an oversimplification (if not flat out incorrect) to say we have nothing like these in the setting.

I'm less sure about sub-Neptunes, being in the setting earlier - that would be a Steve question.

Todd

[AstroChara]

Er. Actually we have:

a) An entire page devoted to super-terrestrial worlds that dates back to 2011 - LINK

b) Panthalassa (LINK), which is a pretty wet place (article written in 2008) and IIRC is also an example of the PanThalassic Type world - LINK (article written in 2008).

Is there something distinctly different about super-Earths and water worlds that clearly makes them not examples of what is described above? At the least, I think it's an oversimplification (if not flat out incorrect) to say we have nothing like these in the setting.

I'm less sure about sub-Neptunes, being in the setting earlier - that would be a Steve question.

Todd

Hmm...oh right, forgot to tell you this: Perhaps most of these 'ocean worlds' described in the article wouldn't have liquid oceans at all - they circle their star way too close for water to be liquid - just high volatile fraction (like >1% or even >10%. Earth, for example, has 0.02% of its mass as water). I know we know superterrestrials are possible, but not their true abundance until not many years ago, hence the rarity of them if you check every described system. I don't think OA has dived into these very common hot water worlds' properties much yet. The concept of liquid water ocean worlds is a lot older.

According to current research, liquid water ocean worlds seem to have a lot of issues with stability, and most would probably rather rapidly end up as either as a Europan (ice increases albedo, world cools down, increases ice, positive feedbacks) or a PelaCytherean (no effective, climate-responsive carbon sink).

[stevebowers]

We have a few hot water worlds (pyrohydrothallassic worlds) such as Wasat
https://www.orionsarm.com/eg-article/4bb5d6c578611
They are common, but they are a little inhospitable for most Terran bionts. Perhaps we could work out a viable strategy for utilising these warm worlds.

One problem is that most lifeforms, and most complex computational systems, work best when there is an energy gradient. There is plenty of energy in a pyrohydrothallassic environment, but it is very well mixed and so the energy gradients are shallow. Any lifeform or computational system that wants to get rid of waste heat would find this a problem on such a world.

[stevebowers]

Here's a few of the ocean worlds we do have in the setting. These are the ones with liquid water surfaces and temperate atmospheres; quite often these worlds are colonised using floating habitats, generally created using carbon allotopes and compounds extracted from the atmosphere.
Panthalassa, Blue, Sarustre, Henson, Donbetyr, Manyanga, FuMa, Rengood;
there are others, and in fact temperate ocean worlds are among the most popular planets for colonisation, since they often have free oxygen in their atmosphere due to photolysis of water.

The more common pyrohydrothallassic worlds are less useful in their unmodified state, although I expect some of them could be modified into temperate water worlds by the use of a sunshade or weather machines.

[Will the Wanderer]

The more common pyrohydrothallassic worlds are less useful in their unmodified state, although I expect some of them could be modified into temperate water worlds by the use of a sunshade or weather machines.

Thanks for the responses. Based off the claim the article makes, they're are hypothetically 1,000 of these "water worlds." It sure looks like OA does have a few, so it's by no means a new idea. But the idea of their abundance seems new. Concerning their usefulness, I imagine those Merpeople and octopus provolves would love them. That'd be about it. Unless I'm misunderstanding how how you're talking about.

Honestly, how do you all keep up with the setting in a constant state of flux?

[Drashner1]

Usually the majority of the flux is additive - meaning its filling in blank spots in the setting or otherwise expanding it - rather than retconning existing content. So that's a bit easier.

The updates of existing planets in response to new RL discoveries isn't as common, although we have been doing it more lately due to The Astronomer's good efforts in this area

In terms of your story - This is a (hopefully minor) challenge of setting stories in the early timeline - having to deal with existing content and canon that might complicate matters. It gets easier with practice and will probably get easier with your story once we get the current core items under discussion resolved.

Speaking of which, I got an idea about your group and the Jupiter boostbeams. Will post it in a bit.

Todd

[stevebowers]

If the surface of an ocean planet is calm enough, and there is sufficient carbon and other trace elements in the atmosphere or hydrosphere to allow growth and/or construction, an ocean planet could be settled using large rafts freefloating on the surface. These could be large enough to allow agriculture or the cultivation of parklands or wildernesses, and the floating platforms could also support cities and other buildings, solar panels, and could collect fresh water from rainfall. Fresh water is lighter than salt water, so could float on seawater if confined within some kind of waterproof receptacle.

In other words the population of an ocean planet need not all be marine clades; there is plenty of room for land-based sophonts as well.

[AstroChara]

Although the paper that contains these discoveries has been out since 2017, the full data only became public later. Here are some of the planets that can be found in this data release.

83 Leonis Ab
Status: Candidate
Semi-major axis: 6.855 AU
Orbital period: 13.020 years
Minimum mass: 0.631 Jupiters

18 Scorpii b
Status: Candidate
Semi-major axis: 3.657 AU
Orbital period: 6.924 years
Minimum mass: 0.337 Jupiters

[stevebowers]

18 Scorpii b would probably be cannibalised by the factions that constructed Felicidade. Either as mass to build the megastructure, or mass to create a wormhole.