The backstory to existence
Written by Gabe
Blink. If you’ve done so, congratulations - you were briefly able to look at a pretty accurate picture of our universe shortly after its creation. Or, at least, of how it would have looked to human eyes. The period the universe entered shortly after its creation is known today as the dark ages, rather aptly named, as visible light didn’t exist yet. There simply wasn’t anything to produce light. All that existed was a “fog” of sorts, composed of hydrogen, helium and extremely small amounts of lithium. This period is thought to have lasted from roughly 400 000 years after the formation of our universe during the big bang until about half a billion years later.
Image: Star-forming region S106 (captured by the Hubble Space Telescope), Techexplorist.com
Eventually, the clouds which filled the universe started to collapse, forming the first stars. The (simplified) process of star-formation is as follows: motion and turbulence inside clouds of gas (or dust) create knots, which, when they have enough mass, attain enough gravitational attraction to cause them to collapse into themselves. Due to this collapse, the material at the center of these “knots” heats up and becomes the core of a star.
Because the universe at that point only contained helium, hydrogen and traces of lithium, the first stars only contained those elements. We call these first stars Population III stars because of exactly that - the comparatively less ancient Population II stars contain more metals and the even younger Population Is contain even larger amounts thereof. To create more elements than the three already mentioned, one needs them to be fused inside the cores of stars, and over time this happens more and more, leading to newer stars having more metals.
An interesting detail is that everything we know about the first stars is only based on deduction and speculation - none have been observed yet, and hence it is thought that most of them are already dead. This would mean that they were much more massive than our sun, since the larger a star is, the shorter it lasts. Our sun has been shining for billions of years and is far from dying, whereas the first stars’ lifespans are probably measurable in the millions (which is quite a short amount of time on the cosmic scale, despite the fact that one million years is much more than human civilization itself has lasted).
The first stars are relevant not only because they were the first ever source of visible light in the universe, but also because they were the forges for all matter other than hydrogen, helium and lithium - a very important element that wouldn’t exist without them is carbon, the key to all life. Without carbon, I wouldn’t be here writing this article, and neither would you, reading it. Because they indirectly caused most of the physical universe to exist, they are of interest to scientists - observing them could garner much valuable insight into how the universe itself actually formed.
How does one observe something that died billions of years in the past, though? The answer to this question is twofold. Firstly, the instrument through which we intend to do that is the James Webb Space Telescope (JWST), a colossus of a space observatory (in fact it is the largest space telescope yet) currently rocketing 1.5 million kilometers away from the earth, which launched on December 25th 2021. Observing the first stars is one of its purposes.
Image: James Webb Space Telescope, TheVerge.com
The second part of the answer pertains to the method rather than the tool. When we look at things, we do not really see the things themselves but instead light that is reflected off of them. Since light needs to travel through space, we really see objects how they looked in the very recent past. This may not be obvious in everyday life, as the time it takes light to reflect off of a pen you’re holding, or the face of a person standing right in front of you, for example, is extremely short, and as such it is almost as if the object in question were observed in real time. However, distance in space is much larger, and light can take millions or even billions of years to cross. Hence, if one were to look at a point that is thirteen billion light years away, they would actually be looking at a snapshot of how that point looked thirteen billion years ago. The JWST is made in such a way that it can be used to observe points distant enough to show us the first stars, despite them not technically existing anymore.
While journalists often refer to the telescope as successor to the older Hubble telescope, which has been very important in many ways - such as discovering new moons orbiting Pluto - over the past few years, it actually differs from it in various ways.
It is much further away from the earth - 1.5 million kilometres as compared to Hubble’s 550 km, which may seem rather humble in comparison. The second, much more important, distinction is that it is focused on infrared light rather than on visible light.
Infrared light is outside of the visible spectrum, and as such we cannot see it. The reason this frequency of electromagnetic rays is preferred over detection of visible light is because the universe expands. The frequency of light waves becomes distorted by this expansion, and as such very distant galaxies are only visible to us in the infrared spectrum.
JWST is a potential breakthrough, as it will allow astronomers to see things that may clarify how matter and life formed in the universe, which has only been answerable by calculations and speculation up to this point. If it discovers the right things, it could bring many revolutionary findings to humanity.
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