OTHER CONCEPTS | THE FIRST INHABITANTS OF THE UNIVERSE (REPOST)

FIRST INHABITANTS OF THE UNIVERSE (?)

This post is an updated version of a previous one (with corrected math and more research) from back in 11/12/2019.

In the blink of an eye, an infinitesimal point (nowhere, since time and space haven't been created yet) which contains everything... Suddenly becomes EVERYthing, just 1 second after the Big-Bang, the early Universe expanded to a trillion light-seconds across, or 33.889 light-years in diameter...

The ambient temperature of this baby universe is about 100 billion kelvin, but don't worry it will cool down over time, and grow bigger... 1 minute and 40 seconds later, the universe temperature is about a billion degrees kelvin... 56 thousand years after, the universe is now at about 9000 K, when it is ~380 thousand years old - the universe becomes transparent and the temperature go down to 3000 K... [source]

At about 15 million years after the Big-Bang, the room temperature of the universe is within the range to maintain liquid water [source]... Even so, there is no oxygen or heavy elements to bound together and make water or either rocky planets. Even if something of the kind did happen somewhere it is short lasted to even support the chemistry that leads to life for more than 2 million years.

THE OLDEST STARS

M37 star cluster

It's fairly dark for at least another 97 million years, until the first generation of stars is born, feeding from hydrogen, growing as heavy as 20 up to (theoretically) a thousand solar masses, stars this big may be up to 1,5AU across, given mass-diameter formula.

Those first stars were absent of metals, which were yet to be fused in their cores and spread through the cosmos as they died in the first supernovas.

As astrophysics tells us, bigger and hotter stars live shortly, and so it is almost certain that such called Population III stars died in a few thousand years after forming. We would need to wait for some more million years for metals to occur in sufficient amounts so planets and Population II stars appear in the record...

As we can take from the Life-Span formula, such a star with 20, 100 and 1000 solar masses would live for approximately, 5,5 million years, 100 thousand years and 316 years, respectively.

Even though second generation stars would be able to form in a hundred million years after the first supernovas, still we have plenty of heavy radiation emission like UV and Gamma Ray from nearby Population III stars and their dead remnants everywhere.

Then, we push the earliest life could have arisen to a billion years afte the beginning of time, the end of the Dark Ages...

The star in which may support such an early life-bearing planet is prolly a 11th generation star, stars like this are still alive today, see Cayrel and Sneden stars.

For Sneden's mass, we have to use a Magnitude Calculator in order to get it's luminosity, and the  derive the mass, which is ~99,12x that of the Sun, what gives us ~3,71 solar masses.

And for Cayrel we find it's luminosity around 94x that of the Sun. which gives us ~3,66 solar masses.

Our hypothetical star will be the average of those, and then we have 3,68 solar masses, 96x the luminosity of the Sun, and it burn at 10.720ºC (sky blue).

Such a star would emit only about 34,4% in visible light, 52% in UV, and 13,6% in IR and Radio, with a color index B-V of little less than ~0,10.

Still, this star would only live for about 340 million years, not even enough for the formation/cooling of Earth-sized planets.

A world around this star would not bear more than 53~55 elements (all the table down to Cesium and a few Uranium and Thorium), still it would have to orbit it's star as far as 9,8AU (as far as Saturn is from our Sun) to be in the Habitable Zone, and would have a 16 year orbit.

As we can see, neither Cayrel or Sneden stars share the same stats as our calculated star, which imply they work slightly differently. Maybe - being so poor in metals, neither all that mass is dense enough that it can get so compact it burns at insane 10.000ºC, ironically, they're more similar to our Sun, being around 4720ºC, (light orange/yellow).

The planet would still have to orbit in a Saturn-analogue orbit (9,2AU for 94 Lsol) to receive as nearly as Earthly possible of sunlight, any closer than 8,2AU and it falls inside the calculated Venus Zone for it's brightness.

I'm afraid to even wonder by what means such stars are still existing, if some star like Cayrel burns at the same rate as our sun, it's initial mass for a 12 billion year long run should have been about 10% more than it is today (about 4 Msol) - for a matter of curiosity.

If any civilization or life ever managed to live around these early stars, my best guess would be low mass stars in low density regions of space away from the larger star clusters, probably on the early galactic edge, and as the galaxies grew up they probably "moved" near the galactic center (as more stars are added on upper layers it "migrates" inward).

Low mass stars can live enough for being around for dozens of billions of years and still if they formed from low density clouds they're probably safe from the immense radiation from nearby novas and early population III stars energy output.

In order to be at least 12,7 billion years old and have at least 2 billion years of life remaining, such a star would need to be 0,8545 Msol or less... Not too far from our Sun's mass, yet, being so massive we can say it would follow a similar path to our Sun, being this old - an enormous and uninhabitable Red Giant or long gone White Dwarf...

Then our next best guess is to opt for a type of star that can live as long as the universe is currently old and still be "habitable"...

RED DWARFS

Red Dwarfs have amazing properties, they are small and can live for up to trillions of years, a hundred times more than the Universe's current age, the only two down sides of red dwarfs is that they are currently very active and thus they vary a lot in brightness, as well doubling it or halving it because of their giant spots generated by their active magnetic fields, which could potentially be harmful for life as we know it - the second down side is that they evolve very slowly, increasing in brightness as their hydrogen brns out - leaving helium behind, and thus when such a star is calm enough to not randomly burn their planets, most of the galaxy's stars will be long gone, and as far as we know it - no red dwarfs are near this phase.

So as we stick with a red dwarf that is as old as 11,5 billion years for example (I'm giving it some time to gather metals and stuff for it's planets, making it younger).

Make it 0,14 Msol and it will likely live for between ~3,5 trillion years, and only then, at the end of its life spend about 5 billion years as a blue dwarf and cool down to a white dwarf.

As we discussed before, red dwarf flares can be 10.000x as powerful as our Sun. Move away 10 AU, and still the atmosphere of an Earth-sized world would be blown away in 6,7 million years, double the world gravity and it will double the effort to rip the atmosphere away, still - 13,4 million years aren't enough, you may quadruple the amount of atmosphere and it will just get to 53,6 million years, even the activity attenuation in this time-scales is negligible.

Using the prediction model for a star like Barnard's Star, it will stay on the main sequence for 2.5 trillion years, followed by five billion years as a blue dwarf, during which the star would have one third of the Sun's Luminosity.

Let's assume that this model holds for the overall population with masses around 0,16 Msol, a little bit above and bellow that.

The model tells us that these stars will be on main sequence for between 559 billion years (0,20 Msol) and +10 trillion years (0,075 Msol). Which means that red dwarfs are on main sequence for a minimum of 99,991% of their lives (99.998% for Barnard's Star).

Going with 0,2 Msol, have about 30% of the Sun's diameter, it will be as hot as 2440 ºC and will likely be on main sequence for about 559 billion years, and this star will have about 9% the Sun's surface area, and shine with 0,357% the Sun's luminosity.

It's theoretical habitable zone would expand from 0,017AU to 0,025AU. While planet formation would not be much probable closer than 0,02 AU.

Any terrestrial planet would likely form between the Cold HZ (0,02~0,025AU) and 0,6AU.

Gliese 3470 - based on Kepler's Third Law and it's only known planet's orbital data, has a mass of ~0,35689 Msol, and then a luminosity of about 2,7% that of the Sun.

Our then calculated Red Dwarf (which I will refer to as AMB3R for now) is much more dimmer than Gliese 3470, 7,5x dimmer and thus could we say it is emitting much less radiation and particles to space than Gliese 3470, instead of being 10.000x as much active than the Sun, it could be about 1.326x as much active or even less -  a quick look at red dwarfs around 0,14~0,27 Msol show that they are flare stars.

Stellar classification based on temperature

RED DWARF FLARES

The closest in mass I was able to find was Ross 614, which may flare almost once per hour, though it had not much further information about it's flare period, Kruger 60 B whoever, doubles in brightness and returns to normal over 8 minutes.

So AMB3R flares once an hour, doubling it's overall brightness and returns to normal in 10 minutes after the pulse, it's overall brightness over long periods would be around 0,416% Lsol (1/6th of the time at double intensity and 5/6th at normal intensity), peaking at ~0,714% Lsol.

Set a 360ºx360º grid on the star's surface and we get a 129.600 square degrees of surface, and as our planet would only be exposed to 360 degrees along it's orbit, there is a 0,27% chance of it being hit if the star is equally likely to fire at any direction any time, 24 times a day - it is about 6,48% chance of being hit at any time.

Our imaginary grid around AMB3R

Let's put a planet, a Super-Earth 6 Earth masses by 2,5 Earth radii, orbiting on the cold HZ at 0,024AU, it's orbital period is then of ~3 Earth days.

Let's start our Red Dwarf habitability discussion here.

- So far, we see low mass red dwarfs have very narrow HZs, which decreases the chances of planets forming in the HZ already.

- Typical Earth-like orbital eccentricity is too radical for such a small orbit, at  0,016 eccentricity, the planet insolation would vary by 80%, alternating between nearly zero and Venus-like, the CO² in the atmosphere freezes one day and on the other, it puffs in the atmosphere just to fall as snow the next day, in order for planet climate being stable around such a low mass star, it's orbit have to be a nearly perfect circle.

- In this case, even considering 2x the greenhouse effect, surface temperatures are about -3ºC, which is bad for liquid water.

Now proceeding...

Now considering flares are pretty slow, about 1500km/s, for a planet that takes 3 days to orbit around it's star, ie, is at 3,6 million km away, it would take about 39~40 minutes for it to reach the planet, the moving of the planet of ~207 thousand km along it's orbit during this time is negligible for reasons I'll show you later.

Updating our chances... 6,48 * 120 = 777,6%

The planet runs through 120º of it's orbit every day, that's certainly 100% chance of being hit at least once a day, more likely around 7~8 times per day.

Now, a study in 2019 was published on the matter of Coronal Mass Ejections as potential Great Filters for advanced technological civilizations, it is possible that some CMEs may reach speeds up to 3000km/s, as we're talking about flare stars, I'll consider that a given, so first reason why I consider the planet movement at this scale is negligible is because this absurdly fast.

Second reason, Carrington-class events can reach levels up to X 1.1 (the one in 2012 did), which is one of the highest solar-flare classifications.

These kind of events, aren't just a blob like small blow through space, they can widen up to millions of kilometers and still be very damaging.

Computer model for the 2012 Carrington-class CME in case it had hit Earth

If we were considering a point-like directional emission for solar flares, we then now have flares that can wipe between 180~90º from the emission point.

If AMB3R is equally likely to fire in any give direction every hour, and considering how disperse and intense CMEs can be at this point, is certain, that any CME on the star's hemisphere that's facing the planet will hit it.

If the planet were stationary, the chances would be clear 50/50, but it does move about 120º in it's orbit every 24 hrs. Every day, the planet basically is exposed to 1,33 hemispheres of the star, if before the planet would be hit by 12 out of 24 flares per day, then now it can be hit by 16 out 24 flares per day.

Even though solar magnetic activity is more common and intense from the 30° latitude on both sides of the equator, at these small scales it is negligible where it does happen, as long is on the side facing the planet.

An X1 CME at 1AU generate an X-ray flux on the order of 0,0001 W/m², which is not so harmful  to humans, though it would be still equivalent to take 8,5 X-ray scans over the course of 10 minutes, a dose of about 0,85 mSv.

It can be lethal for creatures less than 25g in mass.

However, at 0,024AU, the flux is 1.736x more intense, on the order of 0,17 W/m², which is waaayyy more dangerous, a dose of 1,48 Sv if exposed to the full 10 minute flare, sufficient to cause an almost severe case of radiation poisoning, if such a human is around for a second dose after 1,5 hours later, he or she will be certainly dead.

Any living creature under 25kg will certainly die over the first flash.

It is even enough radiation to kill the Thermococcus gammatolerans - a type of Archea that get it's name from Gamma ray tolerance, about 30 thousand Grays, the problem is that for an organism which mass range on the picogram scale, it would be exposed to ≳6 trillion Grays in the first case at 1AU, ≳10,4 quadrillion Grays, on the second around AMB3R.

One may say that it is an overstatement to consider red dwarfs giving Carrington-class flares all the time, but, even with a B1 class flare, the absorbed radiation by present microorganisms is on the scale of ≳6 billion Grays.

There is no way, life could ever arise around such a star giving off such gargantuan levels of X-rays per hour.

And even if it arise in an ocean under a thick crust of ice, it could never go to the surface because there is probably kilometers of ice above, and neither survive in the surface due the intense radiation exposure.

Around higher weight-class red dwarfs, such as M1V and M0V class, is rather probable that life could indeed arise, but it's needed a proper analysis on the activities of these stars to know for sure.

Around M0V stars, a planet with Earth-analogue eccentricity in the mean HZ would have insolation variations of ~16%, however, with an Earth-analogue atmosphere, that means the planet loses water during summer, and nearly freezes during winter, but it is still more habitable than before, and may be even Earth-like if the orbital eccentricity is ≲60% that of Earth.

OLDER POPULATION I STARS

If Population III were the first stars, made from pure Hydrogen, and Pop.II are the metal-poor stars, then we should look at the oldest Pop.I stars around.

Our Sun, can be considered a mid-tier Pop.I star, while Mu Arae is on higher degree having a greater metallicity than our Sun.

High metallicity stars are more likely to have planets around then, tho we can't exactly say stars like Mu Arae or with even higher metallicity are IDEAL for planets, yes there can be planets in those, however, they're more likely to be gas giants or brown dwarfs.

That puts our search for habitable stars with an average metallicity, and slightly older than our sun, and more probably on a similar weight-class, in order to be on Main Sequence time enough for life to develop and flourish.

If we look at solar-analogues alone, we are looking for about 10% of all stars in the galaxy, in 50lyr from the Sun, there are about 10 out of 19 solar-analogue stars that are probably older than the Sun (52%).

There are 11 solar-type stars in 50ly from the Sun, 8 of which are probably older than the Sun (72%).

There are 16 solar-twins in 3000ly from the Sun, 9 of which are probably older than the Sun (56%).

With no repeating stars, we are looking for about 58~60% of the habitable stars around us, with ages ranging from a couple hundred million years older to up to double the Sun's age.

GameTheory did an amazing work about our next topic on this matter.

GREAT FILTERS

Considering 10 Great Filters (or Achievements if you wish):

Habitable Planet

RNA/DNA

Single celled life

Sexual Reproduction

Multicelullar life

Complex Multicelullar life

Tool-Using Animals/Species

Techonological Civilization

Kardashev I~II Civilization

Kardashev II~IIICivilization

Taking a coin-flip for each of those, renders any give planet a 0,1% chance of reaching galactic-scales.

Even so, comparing to the number of stars, such simplistic assumptions would still tell us that 1/1000 sun-like stars do have highly advanced civilizations, and that 20/1000 sun-like stars are inhabited by some sort of complex life-form.

Looking at the ~60% of sun-like stars that are older than ours, this should be about 12 billion stars, 1 billion which may have planets, from which 2,1 million may have life to some degree, using that coin-flip estimate to filter off, gives us 2100 places to look for high-tech-civs.

This may be a rough overestimate, but let's think of how old are these stars now.

Sun-like stars have this 1Gyr window for life to develop into higher degrees before they extinct their habitable planet's atmospheric carbon supply.

Anything older than 5~6 billions years, using the Sun as a model would have been dead, long gone for at least 500 million to 1 billion years.

Planets in the temperate HZ around a 6Gyr old star would have long entered a moist greenhouse effect, losing water to space and even entering Venus-like regimes as the eons go by, any traces of their existence would have been erased from the fossil record by severe weathering in their homeworld, the same applies to their outer colonies, if they have ever settled other habitable stars, they too would go through the same process.

The truth of this, is that if they ever existed, they belong to different time, a distant time almost like a parallel universe, and we're just talking about stars that are a couple hundred million years older than the Sun.

Stars that are billions of years older would have certainly obliterated any traces of civilization by now, they would be so old that isn't even possible for us the listen to their radio signature, as their active bubble would be hundreds of times wider than the Milky Way, and inconceivably dim.

WHAT ABOUT US?

For me, the sheer lifespan of a star can't be out-lived by a species, or clade if you wish.

We have been around for about 250 thousand years, and our genus for around 3~5 million years.

Tyrannosaurus was around for only 3 million years.

Trilobites were remarkably one of the most successful clade on Earth's history, surviving several mass extinctions, and persisting for about ~270 million years, until they finally perished at the end of the Paleozoic Era.

Ginkos been around for at least 270 million years.

Horseshoe crabs been around for about ~440 million years.

Jellyfish also been around for about 550 million years.

Sponges, or at least, sponge-like organisms are thought to be around for at least 760 million years, and counting.

Cyanobacteria been around for about 2,1 billion years already.

However, as you can see, it seems that the longer you can stand, the simpler you have to be, and even that doesn't grant you the geological-lifespan pass, it's easy to say Trilobites, Sponges, or Jellyfish in a general manner, but we are actually forgetting to mention the hundreds if not thousands of species in those clades that have come and gone over time, in order to keep up with the ever changing Earth.

For comparison, the Homo ergaster was one of the most successful hominids to ever walk upon Earth - considering of course it's other contemporaries and the general time-window of other species of the genus. Homo ergaster lived between 1,8 million ~ 750 thousand years ago, some older fossils date back to 2Mya, this is a species lifespan of a full blown million years - this was due a considerably greater ability to communicate, migrate and adapt to new environments than it's contemporaries, even with such low estimated lifespan per individual compared to us modern Homo sapiens.

If we are to ever be as successful as H. ergaster was, that means we probably burned ~1/4 of our natural lifespan as a species, however, the H. ergaster didn't have nuclear weapons, global warming or pollution to deal with, the price we pay for modern society is the ever increasing risk of us messing up everything, or at least, ending up with a self-destructive behavior.

This self-destructive behavior, or some other filter we don't currently know, understand, or don't have control upon, like Gamma-ray bursts, are more likely the things that stops many species from developing further - if we assume life is relatively common, but rare in higher levels - by either pushing them back or extinguishing them completely.

It may be that we humans start an interstellar civilization, on the best scenario - but we won't last enough to be a super ancient species, luckily, we will the be the first step on a long chain of interstellar civilizations, or at least, settle and diversify.

It is then - not far fetched, given our current understanding and view, that the universe is likely full of desert, inhospitable, but habitable worlds, awaiting to be settled, and maybe even, seeded with life.

It maybe that we are just, early arrivals in the great scheme of things, the new archosaurs before dinosaurs were a thing - or are we one of a few incredibly distant and incommunicable civilizations sparkling throughout the galaxy in our time, every one of us and them, empires and entire dynasties of kings, governors, dictatorships, benevolent leaders, thousand generations of archaic and advanced civilizations, all transient flashes in the long scale of our planet's own history, what to say about the universe itself.

If there is something we could leave, that will outlast Earth's habitable window, or even, the Sun's lifespan - are probes, some, remnants of our early days as a space-faring species, some, deliberate attempts to leave a mark away from the weathering and the flintiness of time - frozen in space and time, orbiting our dead Sun, our planets, our outer colonies, monuments to an ancient people that one day, wandered around these distant worlds, so we can say from the distant past...

...we fucked up at some points, please beware.

- M.O. Valent, 29/05/2020