Too Much Stellar Flux: Fixing a 25-year old Problem

[AotrsCommander]

Short version: problems fixing 25-year old world-building; due to canonised data points, I have a planet that is way too hot to work, compounded by interpretation problems by teenage-me on stellar data - help would be appreciated!
Sometime in around the mid 1990s, I got SpaceMaster the RPG (and spin-off of Rolemaster). Among the many thing it had in it was a decent enough system for generating planets and stars, which I immediatley dived into, supplemented by a hertzsprung-russell diagram from an astromy book a friend of my Dad's have given me (which had the advantage over the one in SM that is was larger and in colour). I painstakingly did my best with all the calcuations and applied it to my world building procedures.

Over the years, I have made more than one attempt to make an entirely alien planet. The first attempt was Kethrain, the homeworld of a major power in the universe. The system was generated largely through SM's system and I dutifully did the calculations as best I could. In the end, it gave up on "whole alien campaign world," as being a job too big for the tools to hand and Kethrain just continued as being the homeworld of the Shardan race.

I much later picked up the idea and came to this very forum several years ago for help on number-crunching the second world. (I did really, really well, I felt, in getting all the numbers plausible for what I wanted to achieve with a minimum of hand-wavium... And then ran smack into the problem of solar wind and couldn't even find a way to do some similar level calculations to work it out to be able to even try to tweak it.)

Nevertheless, this exercise was very useful, since while I once again stalled out on that project, the spreadsheet I ended up with is useful for sanity checks for other planets created since.
Now, today's problem is that I am writing up everything in said universe as part of the lore for semi-official release on SpaceBattles and I got to the part with the Shardan.

The first problem was that some of the world-building was predicated on Keth, the star, being green. Because that's what colour an FV5 star was on the hertzsprung-russell diagram in my children's book, and lacking the internet or a proper explanation, I did not understand that is, of course, Not An Actual Thing. (Specifically, the plants are said to be either red or blue foliaged, because they absorb the plentiful green light spectra.) Some handwavium already required, but fair enough, it's mostly cosmetic and work-round-able.

I plugged the existent planet/star data into my spreadsheet.

Second problem.

I had the year length fixed in canon. (Since kind of important when you make even a cursory attempt at history.) Said length based on the calculations I would have done from Spacemaster. (Annoyingly, the paper copy is just about the ONLY thing I haven't found, but I must have had it at some point in-between, since I had all the world data on my insanely large systems and planets list made a few years back...)

The first issue with that it is says in my text that the orbital radius is 1.2AU. Which does not work for an orbital period of 248.125 days on a star of any size - I would not have grocked that at the time, but I would have calculated it - possibly wrongly, though SM had given a simplified formula: square root (orbital radius^3/mass of primary)

But okay, better tools now. So, if I take my data at face value, plug in the values for an FV5 star, with some twiddling of density to Kathrain to 1g, and then adjust the orbital radius with a bit of trial and error to 0.85 AU get the right year length... Cool, it all fitted. Buuuuut...

I get three or four times too much stellar flux. 6776 W/m³, WAAAY too high. There's a bit hotter than Earth on average, and there's (by calculation from that) about 100ºK hotter...!)

(Something of course I would not have had the first CLUE about twenty-five years ago or so.)

For some futher experimentation, even a FV9 was too big and hot, and I got down to about a GV8 (or a interpolated before the stellar flux was in a sensible (Earth-like) magnitude, and an orbital radius of 0.74AU. (Fortunately, said planet is at least the nearest body to the sun, so that's one less issue to worry about.)And now I'm sort of stuck. The star classification and orbital radius are certainly the easiest fixes, but it moves even further away from the "green star" idea.

Reducing the stellar flux doesn't seem like a viable option without the most handwavium, unless there's something I'm missing. (An excessively high albedo is out, since I'm not sure it'd be enough since there's a limit to how much cloud cover albedo can do, especially as Kethrain is not SUPPOSED to be a world buried in a thick fog!)
So if anyone can make any suggestions as to how to do something here, given that the fixed points are a) orbital period of 248.125 standard days and b) stellar flux within habitable range and make a better approximation of the original, I'd be very grateful.

Handwavium on the star or, probably better, something in the atmospheric that makes green frequency light the most prominent seems inevitable at this point, but if there is some other obvious get-around clause I'm missing*, again, it would be welcomed.
Final note, for context, let me paste in the 25-year old, reads-to-be-re-written section on the homeworld:

Kethrain is a medium sized world, 6564.1 km in diameter**. It rotates on it’s axis once every thirty hours - exactly the same length of time as the sunrise-to sunrise period at the equator. It orbits Keth, an F5 green star, in 248.125 standard days, or 198.5 Kethrain days. Keth is eight times brighter than Sol, but a thick ozone layer, and the gravitation pull of the other three stars mean that the amount of light reaching Kethrain is cut down to levels tolerable for life. However, it means that Kethrain is hot, and in the centre of the continents, where the sun shines almost constantly, very dry.

As Kethrain’s orbital radius is only 1.2 AU, the sun appears nearly half as big again as on Earth. Due to the screening of the atmosphere, Keth shines green, but the light it emits is full-spectrum.

75% of the atmosphere is nitrogen, 20% oxygen, and 5% water vapour. Something like 0.5% is carbon dioxide. Radiation levels are higher than on most worlds, but not dangerously so, except in the desert.

There are varied habitats and ecosystems - from the equatorial jungles to the small tundras at the poles. Because Kethrain is warm, there are no real icecaps, and no where life does not flourish.

The Shardan are a careful people when it comes to environmental control, and this accounts for the planet’s relatively low population, which almost all congregate in the cities. What little damage done to the environment done during the industrial age has long since vanished. The combined effect of this is that much of Kethrain is unspoilt wilderness.

During the battle for survival after the Lardatdan died out, the planet was inundated with small groups of bio-technical creatures. However, like their descendants, the Lardatdan had done such a good job of preserving ecological strength that the Shars had to fight for their lives to avoid extinction, even with creatures as powerful as some of those of Caquic. Ultimately, the only ones that survived had to develop something unusual, and that was intelligence. So the only creatures that are now on Kethrain (with only one or two exceptions) are the original inhabitants. All the non-intelligent Shars were wiped out. This just demonstrates the hardiness of Kethrain’s lifeforms. Most are not dangerous, but are much more intelligent that many animals, and are more likely to investigate (cautiously) something new, and they are very resilient in any case. This, perforce, makes the predators even more dangerous. Those that are large enough to attack humanoids can be lethal quite easily, though few will attack without reason. As many of the predators, particularly mechanical ones, use electricity as a weapon, the danger to the inexperienced cannot be understated. Simply put, the life on Kethrain is unique, but the almost tame attitude of the creatures sometimes gives a false impression to the uninitiated - they are not tame, and can be potentially dangerous, so caution is advisable when dealing with any large or unknown creature.

The deserts are very dangerous. Keth beats down mercilessly on the plains, the air is very dry, and the lack of clouds means the temperature can raise up to as much as 86ºC by day, or -40º at night.

Because the light from Keth does is not the same spectrum as on many worlds, the plants on Kethrain take advantage of the more dominant green light, and absorb it instead of other spectrums. Two types of organic plants exist, those that do not absorb the red end of the spectrum (hence appear varying shades of pink), and those that absorb the blue end, thus seeming bluish. This gives Kethrain a unique appearance to it’s flora. This effect is heightened by the mechanical solar plants, which convert the light directly into electrical energy. They have wide, dark ‘leaves’ and are found in the most sunny parts of Kethrain.

(As you can see, teenage-me made a sporting attempt with available knowledge... And this is why years later I always make sure to make my world-building ground work solid enough that this sort of problem doesn't occur...!) *It's been a long, stressful week and fracking about with the lore is about all the Actual Work I'm up to, so it's entirely possibly.

**I very clearly meant RADIUS, since Kethrain is not supposed to be a tiny planet much smaller than Earth. I mean for one, it'd have to have a HELL of a dense core to get up to 1g gravity...!

 

[trurle]

In real world, green-looking sun can be generated by embedding a generally blue-tinted star (F5-class or earlier) into semi-transparent disk of fine dust.

 

[AotrsCommander]

Okay, that's something I wouldn't have twigged (and would actually be consistent with the original FV5 star).

I think one issue though is that all said blue stars are large and hot, sort of by definition, which brings us back to the stellar flux issue. I don't think... Blue dwarfs are a thing, are they? Bringing the heat output down a lot for the orbital radius. (Actually, not sure a white dwarf would put out enough energy for habitability, I'd have to check.)

Highly dubiously... Blue dust over a yellow star...? Doesn't sound vey plausible, on the basis that dust is dust and tend to be like, whitish as a cloud at the best of times...

 

[AotrsCommander]

Okay.

I have had another try at this.

If I say that, for whatever reason, the Shardan measure of time "chal" previously stated to be a planetary year, is in fact HALF the orbital period, that makes things more doable. (Could be a simple diameter/radious confusion in calcualting that years length, in fact, from a quarter century ago, as I look at it now and it looks really short.)

If I push the star to just BARELY above FV6 (so still being an FV5), setting it to a mass of 1.26 Sol, using interpolation, I get a radius of 1.37325 and a temperature of 6375K. A 496.5-day orbital period shoves the OR out to about 1.3 AU (notably close to that 1.2AU from the quoted text, which makes me wonder about that error).

This gives a Stellar Flux of a quite manageable 2173 W/m³. High, but not impossible to deal with. It occurred to me that in order to get the global temperature down to being a bit warmer than Earth (since stabilisaing cloud feedback will not be a factor - I think - on a non-tidelock planet, thus assuming an albedo basically the same as Earth), perhaps some maniplulation of the greenhouse effect might just bridge the last gap. If I reduce to the greenhosue effect from the +33K Earth has (used as a baseline for all the times I've done this) down to 13K, the average global temperature is down to 26ºC (so only 11ºC warmer than Earth). (A 0 greenhouse effect would have the planet be slightly colder, so there's still some room to play with, potentially.)

This, then, potentially solves the green issue too, since we're still on a bluish star; simply add stellar dust to taste.

So the big question now is to first-order hazard what sort of reduction to greenhouse atmospheric composition from an Earth-standard atmosphere would this ential? Obviously a lot of the trace greenhouse gases could be assumed to not be present, but the issue of carbon dioxide, ozone and water vapour are the largest concerns. What would be a way that, either by physical or biological action, could such gases be removed from the atmosphere cycle to keep the greenhouse effect sufficiently low, while retaining a broadly terrestial enviroment? (If this effect can somehow be tied into the dust/green solution, that would be ideal!)

Any suggestions?
At this point, it's reasonably close enough I can do some general handwaving, but if I can, I like to minimise that if I can.

 

[trurle]

You can always add hazes to atmosphere of planet to cool climate. Actually, hazes do form easily as a product of methane photolysis by abundant ultraviolet of F5 star.

 

[Drakkith]

So if anyone can make any suggestions as to how to do something here, given that the fixed points are a) orbital period of 248.125 standard days and b) stellar flux within habitable range and make a better approximation of the original, I'd be very grateful.

Honestly, if you're worried about being technically accurate, the best thing to do would be to go back and make the history work with an altered orbital period. The more you try to alter other things, the more alien your world will be (which may or may not be a good thing, depending on your point of view).

 

[Rive]

Any suggestions?

Don't try to tweak around too seriously. It's better to have a mistake admitted in a footnote, with a promise of a future re-edit than making radiators out of the wings of the X-wing, for example.

 

[AotrsCommander]

Okay.

Taking into consideration what has been said, let me present the current (part of) the draft as pertinent to this topic, to see if I've made any obvious logical frack-ups.

(I originally stated the proportion of nitrogen, but while reading up on hazes - as best I could, a lot of it was really a bit beyond me - I determined that it was probably best not to have stated amount (which would likely be wrong) and have just stuck to stating the breathable components, since to be terrestrially breathable (from doing a bit more looking), you only NEED oxygen in the right partial pressure and the rest to not be, like, actively toxic.)

The Kethsacrad system is a quaternary star system. It consists of Keth itself (FV5), a G7III yellow giant (Sacrad), and a white dwarf (Nadravor) and a red dwarf (Nardrarad). Only Sacrad and Keth have satellites; Sacrad has eight planets and a pair of asteroid belts, while Keth has four and a third asteroid belt. All of the planets and asteroid belts are on non-circumbinary (S-type) orbits.

Nardrarad forms a binary pair with Sacrad, the dwarf forming a distant and erratic ninth satellite, while Keth and Nadravor are singular stars with a mutual barycentre with the Sacrad-Nardrarad pair. It is now believed that Nadravor is the oldest star of the four, initially a solitary star that was gravitationally linked to the forming Sacrad-Nardrarad pair when passing into a stellar nursery, and with Keth itself being captured during its own formation as the system traveled through the young cluster.

All seven of the rock planets in the Kethsacrad system have atmospheres, a factor which is thought to be attributed to the passage through the stellar nursery with the significant amount of stellar dust present.

Around Sacrad, the closest orbiting planet Nardratab is a small world (0.54G), with a hellish atmosphere of chorine. Sacradon is a large rock planet (1.125G) whose atmosphere is a mix of ammonia and methane. Queyilis is hot, but lies in the habitable zone, even having an oxygen/nitrogen atmosphere. According to research, life evolved there for a short time, but for an undetermined reason, lethal bio-toxins began to form in the planet’s atmosphere, and the native life died. Hetrad, the furthest rock planet in Sacrad’s orbit has a thin atmosphere of hydrogen and helium and a variety of trace toxic elements.

Around Keth, Tabmat, a “super-earth” (1.44G) has an atmosphere of predominantly carbon dioxide, with the secondary components being various gaseous acids.

Life has evolved in both the outer gas giants of both stars (Kethmel around Keth and Fourg around Sacrad), but nothing more than proto organisms, primitive plants and simple creatures in the atmosphere.
But it was on Kethrain, the nearest world to Keth, that life evolved and flourished. Kethrain is a HPE-B world. The background magic that sits on the border of Low and High magic, meaning that while magic is known, is it still very uncommon with only a limited number of users. Falling solidly into the –B category, aside from basic habitability (temperature, HPE-breathable atmosphere components and gravity) and ultimately arising humanoid life, it has little else in common with other HPE worlds. The almost-unique nature of the life on Kethrain suggests Harbinger Probability Engineering was almost certainly involved, however.

Kethrain is a slightly larger HPE-B world, with a 6564.1 km radius, but with a slightly lower overall density, leaving it with a gravity that is less than 0.00006m/s² higher than 1g – fundamentally unnoticeable to most creatures. Kethrain has no significant satellites and an orbital period of 496.5 days. The Shardan, unusually, do not use their own orbital period as the basis of their dating system, but instead half of it, a “Chal.” A galactic standard year is 1.47 Chals. However, for consistency, as with the rest of the guide, here dates have been translated to galactic-standard dates and years. Keth has a day-length of 30 hours, thus giving an orbital period of 397 Kethrain days (making 198.5 Kethrain days to a Chal).

Keth is nearly three times brighter than Sol, but the increased distance means that it is only a little brighter and larger in the sky than on a standard HPE-B planet. Kethrain’s upper atmosphere has distinctive haze, composed primarily of spherical haze particles, which affect primarily the visible light spectra. This has two effects. The first of which is to alter the visible light spectra penetrating to the surface, such that the blue star Keth appears green. As the haze complex refracts a greater proportion of the red and blue visible light spectra, the sky does not appear blue, but rather to shade from a paler green to yellow. This effect is not quite strong enough to very noticeably tint the visible light to shade entire planet in green (though there is a slightly greener tinge apparent in some lighting).

The cycle of the haze components in the atmosphere also affects the atmospheric composition, reducing the native quantity of greenhouse gases to only 40% of the effect of a typical HPE planet. The atmosphere is within breathable HPE standards (20% oxygen at roughly HPE-standard atmosphere), but otherwise has a quite different composition to HPE standard, notably with a lower ratio of nitrogen.

Kethrain’s average temperature thus comes out at about 11ºC warmer (a fraction under 300K) than the typical HPE standard (roughly 14ºC). Thus, there are no ice caps. Due to the plate tectonics, Kethrain has a single major continental landmass and only one other major island continent, though it has many smaller island chains. Due to the lower presence of water vapour in the atmosphere, Kethrain is relatively dry, especially in the desert regions of the continents.
However, life is plentiful, due to the almost unique development of Kethrain’s native life. In the super-warm oceans of the ancient past, carbon-based lifeforms evolved, but so did a second contingent of highly unusual creatures.

Their basic structure was similar to the basal carbon-based organisms, but these other creatures used subtly different ways of subsisting. Their outer coating was made of metallic alloys, and instead of DNA they had complicated systems of gold, platinum and silicone. Instead of enzymes, electrical currents were their catalysts. They needed no oxygen to function, but they used hydrocarbons to combust to give them the energy they needed to live. They were a naturally occurring metallic, mechanical life-form.

Over millions of years, plants and animals evolved from these two groups. Where organics evolved bones and muscles, the mechanicals evolved joints and hinges to allow motivation. While organics evolved hearts and blood to carry substances to their bodies, to use the glucose, the mechanicals evolved a complex system of pipelines, combustion chambers, and generators to create electricity. While organic plants evolved leaves for photosynthesis, mechanical ones evolved solar panels.

One other quirk further distinguishes Kethrain’s flora. As the atmospheric haze the upper atmosphere reflects away a proportion of the red and blue visible light from the surface, Kethrain’s organic plant life took advantage of the more dominant green light, and evolved to use that for photosynthesis instead of the ends of the spectrum. Two types of organic plants exist, those that do not absorb the red end of the spectrum, hence appear varying shades of pink, and those that absorb the blue end, thus seeming bluish. This gives Kethrain a unique appearance to its flora.

This effect is heightened by the mechanical solar plants, which convert the light directly into electrical energy. They have wide, dark ‘leaves’ and are found in the most sunny parts of Kethrain and are particularly populous in the desert regions, turning them from what in most worlds would be a more barren place into a thriving high-temperature ecosystem.
But the animal kingdom that was to rise to have prominence in the modern geological period was one composed of both organic and mechanical components. This hybridisation occurred in the very early multicellular stage, and is believed to have arisen from a similar process to mitochondrial or choloplastal evolution. Extensive studies with ever-more advanced technology finally determined that it was the mechanical “eukaryote” that was the engulfing partner. This kingdom remained small and specialised extremophiles for almost 350 million years. (almost half the time that complex life has existed on Kethrain, which has existed for about 750 million years, almost half as long again as that of a typical HPE-L or HPE-E planet). Then Kethrain underwent its largest mass extinction. As the planet recovered from the loss of near 98.5% of its life, one line of this kingdom finally evolved to fully integrate the biological and mechanical components, and rapidly diversified, becoming increasingly dominant in the biosphere.Kethrain’s lifeforms are thus extremely hardy, due to the strong competition. Particularly with the presence of the mechanical element, the evolutionary arms race has included a higher level of intelligence than typically seen on most worlds. While sapience has only occurred on two confirmed occasions, the nonsapient animals are much more intelligent and highly adaptable than typical animals, and are more likely to investigate (cautiously) something new.

This can give a false impression that the wildlife of Kethrain is almost tame, but this is dangerously misleading. Perforce, the predators are more intelligent overall and had to develop many extra tricks, making them extremely dangerous. Those that are large enough to attack humanoids can be lethal quite easily, though few will attack without reason. In addition, many of the predators, particularly mechanical ones, use electricity as a weapon.
It was from the biomechanical hybrids that Kethrain’s sapient species arose. The species now known only as the Lardatdan or Ancient Masters and their civilisation may have been one of the very first to emerge after the Harbingers.

(Astonishingly, the Lardatdan were not even the first sapient species to emerge; just under 850000 years prior, a species known as the Lartaxi (“first people”) emerged, but died out within 50000 years, leaving almost no trace, never having reached much beyond stone age technology.)

The Lardatdan are believed now have appeared around a 67500 years ago and flourished as a civilisation for over 40000 years, at their height being a very advanced FTL-capable civilisation. After such a length of time since their disappearance, information is scarce, but the Shardan have made extensive archaeological efforts over the course of their own civilisation.

What is known is that technology was (at least for the majority of their civilisation) all very environmentally friendly. With very few hydrocarbon deposits to burn – as many mechanical species consumed these – their technology, like their world, was a mix of organic and mechanical. Their territory once spanned quite far into the galactic core, but little towards what is now human space, which is why few traces have been found. Most of the remains lie in Lyrokana or former Strayvian territory. The Lardatdan settled very few worlds, with most of their ruins being space-stations or domed installations on uninhabitable planets. The Lardatdan seemed to have actively avoided contact with other alien powers (intelligent or otherwise), due to the pervading beliefs of their culture.

This insularity ensured that their sudden collapse was almost total. The precise reasons for this are almost as much a mystery as that of the Harbingers and while over the centuries, many theories have been forwarded, none have proven satisfactory. The Shardan, whose technology would easily encompass time-travel, have been traditionally loath to use it to explore the Lardatdan, out of respect and due to a significant possibility it was some form of advanced pandemic that might be brought to the future. (Aotrs intelligence suggests that the truth may in fact be known to the Shardan, or at least their leaders, but if so, it is not publically known.)

Overall context notes: In very, very brief, the Harbingers are the oldest known civilisation which disappeared about a million year ago, and are noted as having used retrocasual probability engineering to basically make lots of planets with terrestrial-like atmospheres have happened. Such worlds are now designated as HPE worlds (Harbinger Probability Engineered); Earth is an HPE-E. (As to why nothing predates them, it is strongly implied that they used retrocausally ensured there couldn't be, with retrocasual probability engineering fundementally making the universe be the way it always was.)(A fuller (much, much longer) explanation is on this thread on Space Battles, which I link only for completeness or if you are somehow interested and have a lot of time to kill, since it doesn't have any direct bearing on this particular topic.)

 

[trurle]

I have 3 points:
1) Chlorine atmosphere is not feasible. It actually more susceptible to atmospheric escape than more common carbon dioxide. If you need some hell on hot planet, sulfur atmosphere is option for over 450C (just over temperature of Mercury)
2) Gold and platinum would be extremally rare on Kethrain, given its size and density. If you need to start metallic life, silver and copper are more available start elements. Gold coatings may evolve later though.
3) Evolution of electrical cells (batteries) is missing. Also, rather than combusting hydrocarbons, will be easier to evolve predation to get dissimilar metals (zinc and silver, for example) from metal plants and use these metals in battery cells.

 

[AotrsCommander]

I have 3 points:
1) Chlorine atmosphere is not feasible. It actually more susceptible to atmospheric escape than more common carbon dioxide. If you need some hell on hot planet, sulfur atmosphere is option for over 450C (just over temperature of Mercury)

Noted and changed.

That is 100% SpaceMaster's fault, as the Kethsacrad system was generated entirely from the random tables therein. I point directly at SpaceMaster 2E's random atmosphere table entry: "41-60: Predominantly Cholorine."

They may not have known that in the 1990s, and it certainly would not have been as trivial to research before the Internet was a singificant thing, of course.

2) Gold and platinum would be extremally rare on Kethrain, given its size and density. If you need to start metallic life, silver and copper are more available start elements. Gold coatings may evolve later though.

Edit: didn't twig until I re-read the offending paragraph that I'd specifically mentioned gold and platinum in the make-up section, which as I re-read it and it sunk in... Yeah, doesn't make a lot of sense, really, and I have NO idea why I wrote that... Presumably, I had read or talked to someone that suggested it for the properties - but copper and silver are better - or from some half-idea that was Lootable Body Parts or something. While the following stands as a point about how much mineral gold and platinum in likely in the core, I do actually concur with your point with regards to physiology and have made said changes!

Kethrain's density is not THAT much less than Earth (5435.6 kg/m³ compared to 5515kg/m³ about 98%) - it's "only" about 4% bigger by volume.

But, considering the time exotic materials have been factored in; plus factors arising from the background magic level (which aamong other things in the other parts of the lore I hadn't posted strongly suggest the presense of some sort of "underdark" equivalent would be present as on many High background magic HPE-L ("fantasy") planets) and almost certain implication that Harbinger Probability Engineering functionally forced the statistical probabilties of element formation (along with everything else) into basically "this result is intended...*" I'm not going to lose too much sleep about this one, on balance. Though I will, as always when this sort of thing is brought to attention, bear it in mind.
*Technically, HPE-Bs are theorized to be the... spill-over? As it were from creating one of the (at least) two paradigms the Harbingers apparently saw fit to perpetuate; in which to create those, the HPE-Bs are thought to be analogous to being basically the rolls that were not quite the desired Natural 20s, as it were.
Heck, said probability engineering could (and likely did) easily bias the crust-to-core proportions of any element composition to achieve that the Harbingers decided was The Right Balance, so even if the platinum group is rarer in the core, it might be slightly less so on the surface.

(Kethrain itself was once a candidate for "fantasy campaign, but its on an alien planet with biotech aliens" at the time, which is why this write-up is taking me SO LONG and why I abandoned that idea, since with the tools and data I had at the time, it was - as re-writing has shown - just too many holes.

Case-in-point. later today, the next job is re-twiddling the calendar because in the late 90's, there wasn't enough information to make an educated guess on technological advancement timescales (or even my own starship wargames rules to be able to estimate a ball-park credible rate of advancement) and I was way, way, WAAAAY off. To get from the time point of one canon event that happened in the technologically-late-1980s to present (top of the galaxy advancement) the dating system was out by about by about 2000 years (and 3000 Chals). Far from the current calendar being started around 1500 years earlier than technologically-late-1980s, it needed to be about 250 years earlier in order to credibly fit in what is estimated at over 4000 years of post-FTL development advancement. The Shardan have technically still cut off 600 years from the admittedly VERY loose projections, but even the loose numbers attached provide a right-or-at-least-relaively-mostly-consistent-ball-park progression over time.)

3) Evolution of electrical cells (batteries) is missing. Also, rather than combusting hydrocarbons, will be easier to evolve predation to get dissimilar metals (zinc and silver, for example) from metal plants and use these metals in battery cells.

That section was somewhat hyperbolic (and also not much changed from original writing) rather than explictly accurate; batteries are, I think, somewhat implied (solar plants have to store their power somewhere, after all). That comparitive list was intended to definitely be neither exhaustive or all-inclusive. But again, noted, as it is a point I would not have known to consider during the first writing.

That said, there is also a reasonable defense that what exists in (some parts of) the modern fauna and flora will not be the totality of what evolved (Kethrain's evolutionary history of complex life being about half as long again as Earth's). Once again, there is an element of probability (admittedly, this time likely geninue, not HPE'd) at play in evolution. I will postulate, then, that the hydrocarbon-consumption lineages developed in the aftermath of the largest mass extinction due to the surivivors being by nature mostly extremeophiles (less affected by the global conditions) or highly-adpatable generalists, one or both evolving to taking advantage (at some point down the line) of the masses of hydrocarbon desposits formed from said mass extinction event.

So likely there are groups of creatures which eat hydrocarbons and/or dissimilar metals or even both. If anything, Kethrain's environmental pressures are likely to have resulted in a much wider varienty distribution of kingdoms of complex life than on Earth (over the course of history, of course, and it's very possible not all of those kingdoms survived to the present).

(Hell, I could make a reasonable argument that maybe the hydrocarbon eaters might perhaps have been just one extinct lineage that achieved popular consciousness (akin to to dinosaurs) and would have demanded inclusion in such a list or be notable in their omission. But at that point, it would likely require going even deeper into Kethrain's total evolutionary history... And that kind of effort is something I would prefer to be spending on Andorlaine, where there remains a chance that it might see usage; and I stalled out on that a while back.)

Nevertheless, I have amended that sentence to "They needed no oxygen to respire, but instead they used it and hydrocarbons to combust or the differing charges between metals to give them the energy they needed to live, sometimes stored in natural batteries."It is worth noting perhaps that "take this (seemingly simplistic) thing written at face value, and then how/why has it arisen" and working out the complex causes and logic behind it has been something of a defining characteristic of the whole lore project. Which has produced a lot more depth, because, after all, such instances then become a point to talk about and explain. When/if something has turned out to Be Totally Wrong (that's not easy to gloss over and/or retcon like a minor point like a system's planet's atmosphere being wrong), some attempt has been made to say, "this was initially thought to be [x] because [y], but turns out, it was actually [z]."

(And, of course, leaving a good few old-fashioned mysteries, because sometimes the best explanation is "actually, nobody knows" with some "but it is theorhised that..." Which is why all the lore stuff I do is always written, as it were, from an in-universe stand-point (subject to revision and error over time), rather than meta-objective fact from beyond the forth wall. This approach can also be 100% blamed on Stewart Cowley's Spacecraft 2000-2100AD, which stuck in my head and permenantly altered how I see things.)