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
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 burns 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 2480 K and will likely live for about 1 trillion 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 0,053AU to 0,18AU. While planet formation would not be much probable closer than 0,02 AU.
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.
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.
Building a 360ºx360º grid on the star's surface we get a 129.600 square degrees of surface, and as our planet would only be exposed to 360 degrees on it's orbit, there is a 0,0027% chance of it being hit if the star is equally likely to fire at any direction each time, 24 times a day - it is about 0,0646% chance.
Assuming only flares fired directly at the planet would be harmful - and that it would, the planet may be hit 23,25x per local year (for a planet at 0.095 AU).
Now considering flares are pretty slow, about 1500km/s, for a planet that takes 25 days to move around it's star, it would take about 6,6 days for it to reach the planet, when it will be nearly as 95 degrees ahead of the flare, still, if we now consider only the ones fired at the right inclination and towards to where the planet will be in 6,6 days, the chance still pretty much the same, this world would be certainly exposed to 1 flare a day.
Now, solar magnetic activity is more common and intense from the 30° latitude on both sides of the equator, updating our grid, it gives us 21.600 square degree to pick from, which takes our odds of being hit by a flare to 138,24x per local year, or at least 5,5x per day.
Flares that would reach levels of energy on the order of 1,32E23 J (132 zettajoules) or greater. Coronal matter of our sun is about 1 million K, though, the black body radiation calculator only accept inputs up the order of 10.000 K, which seems good enough as heat radiates away in space and the amount of mass in a flare may also distribute the heat and our star isn't that hot as well, according to that model then, AMB3R's flares would emit 2.01365e+16 photons per joule on the 400 picometres wavelength, and looking at how many joules we have, the flare generates up to 4.43003e+36 photons of X-ray, which if we distribute towards our planet using the inverse square law and the given value of 5.5691e+20 phot/s/m² as a base, gives us 0.0137x what we started with - or about 7.6297e+18 phot/m², which is incredibly dangerous, as this is 8,47... S E X T I L L I O N times more intense than an X9 solar flare.
~3,792 KJ per square meter, a human body area facing the star at this moment may be around 1/2 it's total body area, or about 0,95m², and may weight about 75kg, which gives us an exposition to 48 Grays of radiation - per second... for about 10 minutes... 29.100Gy in total... That's taking about 41,5 million X-ray scans, in just a couple minutes... Tobe exposed to an event like this, for just one second, is already 10x the required lethal dose of radiation for a human. It is even enough to kill the archaea Thermococcus gammatolerans.
Even if biology on this world somehow miraculously evolved to survive such radiation levels - electricity technology would be a struggle, if not impossible, they'd have long collapsed under their scientific limitations or be swept away by time eons ago...
X-rays and UV radiation emitted by solar flares can affect Earth's ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies [...]
Short answer to ultra ancient civilizations, NO, long answer, I dunno, but as far as we know, it is a big NO.
Fun Fact
The most voluminous red dwarf is on the AU Microscopii, which is on the constellation of Microscopium (Microscope).
And today it's my 18th birthday :)
- M.O.Valent, 11/12/2019
