Within astrobiology discussions, the term habitable zone often comes up.
There are several types of these general zones, but also special cases such as ice shell moons
where life may be possible completely outside of a standard stellar habitable zone.
With stars, this zone, also called the goldilocks zone, is a section of space around a star
where planets could be warm enough to harbor liquid water on their surfaces.
Earth, for example, sits within the sun’s habitable zone.
These zones vary by the type of star, so the habitable zone of a red dwarf star is very
close in due to how dim they are.
As we deal with larger classes of stars, this zone is located further outward, and indeed
when the sun swells to its red giant phase, it’s habitable zone will likewise migrate
outward as well.
There are also concepts such as a galactic habitable zone, where conditions allow for
life and civilizations to arise in principle, but outside that zone, such as in the center
of the galaxy, it becomes far less likely due to the harsh environment present there
due to the stars being more closely packed in.
But there is now new thinking on yet another type of habitable zone where the entire universe
was once warm enough to support liquid water on the surfaces of planets regardless of whether
they were even near a star.
In a paper by Abraham Loeb, link in the description below, he lays out the idea of a habitable
epoch within the early universe.
Very early in fact, opening up the possibility that just a mere 10 to 17 million years after
the big bang it’s hypothetically possible that some form of life could have had its
genesis within the universe.
The question here is just when the earliest stars formed, and what happened after.
The oldest stars we still see in the universe formed about 200 million years after the big
bang.
However, one of these ancient stars, called the Methuselah star, even for its age appears
to contain heavy elements which would have been created in supernova explosions from
even earlier stars than this.
Also, quasars are also seen to have metals in their spectrum and other evidence pushes
the date back to about 180 million years after the big bang when the first stars, conventionally
speaking, formed.
Planets would then come after that as heavier elements are created by those stars.
But there may be another way where very large stars, and planets, could have formed much
earlier involving the interaction of dark matter.
If so, these very earliest massive stars would have produced heavier elements pushing back
the possibility of planet formation very early in the universe.
If this was the case, then those planets could have hosted liquid water on their surfaces
just from the warmth of the afterglow of of the big bang itself.
But this period would not have lasted long, only about 6-7 million years before things
cooled off to the point that habitable zones around stars would have started to take shape
and the liquid water freezing on worlds not within them.
It’s anyone’s guess if this is enough time for life to arise, but we do know that
if earth is any indicator, microbial life’s advent on earth happened essentially the first
moment it could.
If that’s standard, then simple life could in principle have existed just after the big
bang, at least for a time.
And if one of those early hypothetical planets happened to be within the habitable zone of
its star to the point that it’s still around and has maintained the conditions for life
the entire time, then it could be, though probably a long shot, that there are planets
with life out there nearly three times older than earth.
Imagine what an ancient civilization perhaps approaching 10 billion years old might look
like.
Thanks for listening!
I am science fiction author and futurist John Michael Godier currently planning a vacation
of sorts.
This coming June in conjunction with astrotours.com, link below, I will be joining Paul Sutter,
Fraser Cain and other science youtubers for the All Stars Star Party at Joshua Tree National
Park.
For details, visit astrotours.com and no I won’t be driving the LeBaron cross country,
I think it would make it, it only has 300 thousand miles on it, but why put undo wear
on the interiors and be sure to check out my books at your favorite online book retailer
and subscribe to my channels for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.