What came before the stars?
We live in a universe that is full of bright objects.
On a clear night, thousands of glistening stars can be seen with the unaided eye.
But these stars only occupy a tiny part of the Milky Way Galaxy.
Beyond, the Universe shines with the light of trillions of other galaxies, each containing
billions of stars.
But what came before the stars?
And how did these dramatic objects burst into existence?
According to the Big Bang theory, 13.8 billion years ago, time and space began.
The building blocks of everything we see today burst into existence.
No one knows what came before this moment.
It is the point from which our understanding of the universe breaks down.
But despite the mystery of how it all started.
Researchers have been able to piece together a rough timeline of the major events that
came after this incredible moment.
Unlike its name suggests, the Big Bang wasn't an explosion in space but rather a period
when the universe was extremely hot and dense, and space began to rapidly expand in all directions
everywhere at once, faster than the speed of light.
Soon after, the universe would have looked opaque.
It would have been like a hot, dense soup of particles, including protons, neutrons,
and electrons.
When the universe started cooling, the protons and neutrons began combining into ionized
atoms of hydrogen and some helium.
Under these extreme conditions, the matter would have been distributed like a thick fog
throughout the Universe, scattering the light.
After 380,000 years or so, the ionized atoms of hydrogen and helium eventually attracted
electrons, turning them into neutral atoms, allowing light to travel freely for the first
time.
This process of particles pairing up is called "Recombination" and is the point when the
Universe went from being opaque to transparent.
Light had formerly been stopped from travelling freely in the early opaque universe because
it would frequently crash into free electrons.
Now that the free electrons were bound to protons, creating neutral atoms, light was
no longer being impeded and could travel in straight lines.
This set loose the flash of light created by the Big Bang, which is detectable today
as the Cosmic Microwave Background.
The earliest possible snapshot of the universe.
This is an image of the universe just 380,000 years after the Big Bang.
The stars, galaxies, planets, and other objects we see today when we peer out into the cosmos
did not just pop into existence after the Big Bang.
It would take hundreds of million years before even the first stars began to ignite within
the first protogalaxies.
But before the age of starlight, there was a time when the universe was completely dark.
This point in time is called the cosmic dark ages, a period after the universe became transparent
but long before the first stars formed.
For several hundred million years or so, nothing in the universe gave off light.
But the universe wasn't empty.
Matter created by the Big Bang began to clump together, pulling in ever more material through
gravitational attraction.
Eventually, crisscrossing the dark void was a vast structure called the cosmic Web.
These enormous threads of gas may have also been created in part by interlocking filaments
of dark matter, an elusive, undetectable substance in the universe.
But it is within these threads of gas where the first stars, the ancestors of our Sun,
ignited into existence.
As the thick clouds of gas in these areas became denser and denser, it began to collapse,
and in the densest regions, the gas became so hot that nuclear fusion reactions began.
And out of the darkness, the dawn of starlight emerged.
The Universe was finally illuminated.
The first stars to ignite in the Universe were probably enormous objects made almost
solely of hydrogen and helium, the elements that formed as a direct result of the Big
Bang.
They would have contained none of the heavier elements like carbon, nitrogen, oxygen and
iron that are found in stars shining today.
They were likely hundreds of times more massive than the Sun and burnt with such ferocity
that they shone bright blue, with the energy of more than 1 million suns.
Because these Titan-like stars were probably extremely large, they would have burnt through
their fuel supply very quickly.
A star 60 times the mass of the Sun, for example, is estimated to last less than one million
years.
This could mean that the first stars, known as population three stars, exhausted their
fuel supplies long ago, exploding in a magnificent cosmic event called a supernova, and now can
only be observed as remnants, such as neutron stars or black holes.
When they died in supernovae explosions, however, they would have produced the first metals
for the following population of stars, called population 2, which have a small proportion
of metals.
Metals being the term that astronomers use for anything heavy than hydrogen or helium,
by the way.
These then went on to birth the metal-rich population one stars we have today.
Since the very first stars emerged, trillions have existed.
But ours could well be the most unique out of them all.
It is possibly the most extraordinary.
Why?
Because our star, the Sun, nurtures the Earth, the only place, as far as we currently know,
which allows life to exist, and in our case, intelligent life that can study the Universe
and discover what might have happened during those first moments that eventually lead to
our own existence.
This is the incredible cosmic connection that we all share.
Because, after all, every human that has ever existed came from the dust of these ancient
stars.
What do you think of these ancient Giants?
Let me know in the comment section below.
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