What is significant about this very specific period after our Universe's formation? According to the study, the cosmic microwave background provided a uniform heating source that was between 0 to 100°C (the melting point and boiling point of water at 1atm) during 10-17 million years after the formation of our Universe. This means that there was no Habitable Zone around stars since the entire Universe was one gigantic habitable zone (except maybe being too close to a star).[001]
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| Hypothetical earliest stars in our Universe |
Challenges for Earliest Stars and Planets
There's a catch. Stars that formed immediately after the Big Bang were very different than the stars we now see. The only two elements available in the Universe were Hydrogen and Helium. These early stars are referred to as being metal-poor, lacking access to elements heavier than than Helium. There is speculation that the very first stars where actually extremely metal-poor. Material from which terrestrial planets could have formed simply wasn't available yet. When these first stars died, they produced the elements necessary for the formation of planets and metal-rich stars. The death of these stars had to happen very quickly in order to meet the criteria necessary to consider life being possible so early in our Universe's existence.In order for rocky planets to exist at these early times, massive stars with tens to hundreds of solar masses, whose lifetime is much shorter than the age of the Universe, had to form and enrich the primordial gas with heavy elements through winds and supernova explosions.[001]Cosmic simulations suggest the formation of massive early stars that explode relatively quickly.[001] Gravitational lensing also suggests the formation of such stars in the earliest galaxies.[002] Given the possibility for such stars and such explosions of such stars, planet formation early in the Universe was also possible.[001] Given the cosmic microwave background heat of the Universe, the likelihood of planets with water on their surface was again also possible.
On the plus side for these planets, once the cosmic microwave background cooled down after the 17 million year mark, the planets themselves may have been able to keep warm enough on their own for quite awhile, even without a nearby star.
[Thermal gradients needed for life] can be supplied by geological variations on the surface of rocky planets. Examples for sources of free energy are geothermal energy powered by the planet’s gravitational binding energy at formation and radioactive energy from unstable elements produced by the earliest supernova. These internal heat sources (in addition to possible heating by a nearby star), may have kept planets warm even without the cosmic microwave background, extending the habitable epoch...[001]
Speculation
Although the study The Habitable Epoch of the Early Universe suggests that life may have been possible in the early Universe, much of that life may not have survived past 17 millions years after the Big Bang unless it was lucky enough to be in the Habitable Zone within a solar system that included a very stable star. However, even if the life didn't survive, the organic matter from which the life formed may have survived. The survival of this life or its material could have seeded the later Universe, drastically increasing the chances of life reemerging. Some speculate life on Earth originates from extra-solar system sources. Perhaps the material necessary for the emergence of life was already in the mix from which our Sun formed. The mechanism for such transference of life and materials is called Panspermia, or specifically, Pseudo-panspermia and Lithopanspermia.
It seems there would have been a substantial gap between the first wave of early life and the next wave of life; this next wave presumably being the epoch within which we find ourselves now. How might species from the early epoch be viewed by species of the current epoch?From a Science Fiction perspective, such early life may have evolved to sentience very early in our Universe's existence. Being so close to our Universe's beginning and having so long to evolve may have allowed these early species to development god-like powers by now. Such species may be Q of Star Trek: TNG, Time Lords of Doctor Who, Nibblonians of Futurama, and perhaps less god-like Precursors of Star Control II and Progenitors, also of Star Trek: TNG.
Would signs of god-like species be discernible to us young species? We wouldn't likely see evidence in the form of direct radio signals, as such species would have long since evolved beyond such primitive methods of communication. Perhaps we could catch a glimpse of these early species in the earliest days of their development via EM signals they emitted billions of years ago, from distance galaxies.
We'd have to know where to point our detectors. Signals from ancient civilizations within our own galaxy would have passed us by billions of years ago. However, signals from ancient civilizations in galaxies billions of light years away would be reaching us at the same time as the rest of the light from those galaxies. Such signals would be faint and scattered, but they may be just distinct enough to discern from the background noise. For example, at certain times of the year, Earth glows at certain EM frequencies much brighter than any other object in our galaxy. A similar civilization billions of years ago in a galaxy billions of lights away might be obvious to us once we start looking for such phenomenon.
The idea that life may have developed so early in our Universe's existence opens up a Universe of possibilities. Our understanding of our origins may be even effected by this concept. On the other hand, maybe life in our Universe wasn't possible at all until very recently. Maybe we are one of the first species to develop sentience in all of the Universe. I'll cover more about this in a later article.
Primary reference:
A. Loeb, International Journal of Astrobiology, 13, no. 4, (Sept., 2014), arXiv:1312.0613 [astro-ph.CO], The Habitable Epoch of the Early Universe
Response:
Hacker News
Article Series:
- Limited lifespan of Habitable Zones around other stars [and a loosely held secret finally revealed about me]
- Small stars may have stable Habitable Zones, but habitable planets might not be common there
- Habitable Planets around White Dwarfs
- Habitable Worlds Around Binary Star Systems might not match Sci-fi
- How many Earth-like planets are orbiting Sun-like stars?
- First round of life in the Universe might have been possible extremely early
- Factors a planet needs for suitability of life; perhaps
- "Goldilocks zone of metallicity" on a galactic scale
- Maybe we are the first
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