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The first light in the universe

James Webb Space Telescope observations of galaxies in the young universe revealed that the first light in space came from bright young stars

By Amit Pandu, Davidson Institute for Science Education website

The galaxy cluster Abel 2744 or the Pandora cluster. The researchers looked at the galaxies behind it. Photograph of the Hubble Space Telescope
The galaxy cluster Abel 2744 or the Pandora cluster. The researchers looked at the galaxies behind it. Photograph of the Hubble Space Telescope

Many stages in the early life of the universe are not precisely known to us. One of the mysteries concerns the appearance of the first light sources in the universe, which we manage to see. New research, which is based on observations by the James and Webb Space Telescope, suggests that those sources were young stars that were much brighter than scientists had thought.

Why does the universe look the way it does? This is one of the open questions in astrophysics in particular and physics in general. In the first billion years of its life, the universe transformed from a disorderly soup of high-energy particles into a more organized collection of galaxies and stars, but many details of this process are not clear to us. In the new study, an international group of researchers analyzed observations by the James and Webb Space Telescope of dwarf galaxies from the early universe, and it shows that these galaxies emit a much stronger beam of light than expected. The research is a breakthrough in our knowledge of the first light sources in the universe.

A brief history of heat in the universe 

Immediately after the big bang, the universe expanded rapidly while being hot and with very high energy: the average temperature of the particles in the universe was about 1030 ° C. At such a high temperature, subatomic particles cannot connect to each other, and there was no material in the universe that resembles the particles we know today. After about one second, the universe had time to cool to a temperature of about a billion degrees, and the subatomic particles which we know from the standard model formed, combined and produced protons and neutrons. 

When the universe was twenty minutes old, it had already cooled to a warm temperature of hundreds of thousands of degrees Celsius, and the protons and neutrons began to combine with ions of hydrogen, helium and lithium. Because of the high temperature of the universe, the particles still had very high energy, so the electrons could not combine with protons to form atoms. As a result, most of the universe was composed of plasma - a state of aggregation of electrically charged particles flying around each other. The plasma is sealed to electromagnetic radiation, so light could not propagate in the universe. 

During the next 370 years, the universe continued to cool until it reached a temperature of about 4,000 degrees. It was cold enough for the electrons to join the plasma and form neutral atoms. The cosmic background radiation from which we learn about the early universe is the radiation that was released at this stage and that managed to travel a great distance until it reached us, since there is no longer any plasma to stop it. 

Viewing the early universe through gravitational lensing. Figure Stark/Ellis with Caltech Digital Media Center
Viewing the early universe through gravitational lensing. Figure Stark/Ellis with Caltech Digital Media Center


How light was born

At this point, when the universe was nearly 400 years old, it was mostly composed of neutral atoms of hydrogen and helium that were fairly evenly distributed. There were no stars, galaxies or any other complex body that we are used to seeing when we look at the sky. In particular, there was no light source. The universe was dark.

Only about 20 million years later, when the universe expanded and cooled significantly, the first light sources in the universe were created. Astrophysicists who study the history of the universe do not know the nature and origin of these light sources, when they were created and how. Their hypotheses regarding the first sources of light in the universe included large black holes, massive galaxies, or young stars. Unfortunately, there is still no established theory of the formation of stars and galaxies in the early universe, and physicists are trying to understand when and how the first light sources appeared in the universe.


The dwarfs are four times brighter

The researchers used In the James and Webb Space Telescope, launched in late 2021 in order to observe very distant galaxies. Light moves at a finite speed, so it takes a long time for light from distant galaxies to reach us. The researchers observed light emitted from galaxies about 13 billion years ago and reaching the telescope today. This is how researchers can learn today about processes that took place in the early universe. 

The galaxies are far away and appear to us as they were billions of years ago, when they were young galaxies and emitted little light compared to the rest of the celestial bodies. As a result, it is difficult to observe such distant galaxies in standard ways. That's why the researchers used a clever ploy: According to Einstein's theory of general relativity, heavy masses can distort space and cause light to change its path. The researchers only looked at the galaxies behind the massive galaxy cluster Abell 2744. The cluster's mass is so great that it can act as a lens and focus the light coming from behind it. This way the researchers could increase the amount of light that reaches the telescope and make more accurate observations.

The researchers analyzed the light coming from dwarf galaxies - galaxies that contain only about a billion stars. For comparison, the Milky Way galaxy we are in has hundreds of billions of stars. The researchers carefully analyzed the observations and discovered that these dwarf galaxies emit radiation four times stronger than previously thought. Moreover, in the early universe these galaxies were much more common than large galaxies. As a result, the researchers speculate that most of the light sources in the early universe were galaxies of this type.

The study is another example of a scientific breakthrough originating from the telescope and. The results of the study are significant, but the researchers point out that much more work is needed - among other things, the researchers are interested in observing a wider sample of galaxies to strengthen the plausibility of the study's conclusions.

Davidson Institute website

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8 תגובות

  1. "The average temperature of the particles in the universe was about 10 to the power of 30 degrees Celsius. At such a high temperature, subatomic particles cannot connect to each other, and there was no material in the universe that resembles the particles we know today. About one second later, the universe had time to cool to a temperature of about a billion..." According to this theorem, it cannot be concluded that the temperature in the universe cooled by 10 to the power of 20 in at least one second, but later on it is stated that the rest of the universe was 20 minutes old, the temperature dropped by less than 10 to the power of 10. This ram Is it possible or did I understand correctly? It seems to me that the sentence I deduced makes a lot of sense, but the second statement contradicts it. Can someone explain?
    Here is the quote: "When the universe was twenty minutes old, it had already cooled to a warm temperature of hundreds of thousands of degrees Celsius...".

  2. Thanks for the article. Nicely written and clear. I have a question about another article where they wrote about trying to understand the structure of the young universe from gravitational mixing of cosmic radiation. I don't understand it and maybe you can explain it to me. Cosmic radiation is the first light released after the universe cooled. So this light came out long before stars and galaxies started to form. So how is there a gravitational field that affects the observed cosmic radiation?
    Thanks

  3. @ Yotam (the first commenter)
    The clusters of galaxies with a huge mass like Abell 2744 are used as a certain type of magnifying glass that allows us to observe distant objects with increased resolution compared to the most sophisticated optics we have today (although it is not free from geometric distortions).
    You can do a simple experiment at home: take a 10 AJ coin, look at it in the air and measure its size by eye. Now put the same coin into a transparent glass of water and compare the size...the coin looks big compared to the air despite its slightly distorted shape. This happens because the mass of water is heavier than that of air. Now think about galaxy clusters with a mass of ...

  4. Just asking where the call in question came from
    Was there any natural law in the universe that when there is warming there must be cooling
    What cooling the high heat
    This is more accurate
    that because we are used to the concept of heat and cold that exists today
    After all, it wasn't at the beginning of the creation of the universe (according to the big bang hypothesis of course) that the laws of physics known to us did not exist.
    So he filled in on the assumption that there was a map.
    How do we do cooling?

  5. You are not coherent in the article.
    On the one hand, you write that
    The protons and neutrons began to combine with ions of hydrogen, helium and lithium. Then you write that it was too hot and the electrons could not connect to the protons and form atoms. I don't really understand the logic here. But this is not the only thing that is not clear. You go on and point out
    that as a result, from the immense heat, most of the universe was composed of plasma - a state of aggregation of particles with electric charge flying around each other. The plasma is sealed to electromagnetic radiation, so light could not propagate in the universe. I mean because of the heat, that's what happened.
    Taz Hiktam cooled down over 379 thousand years to a temperature of 4000 degrees which allowed, pay attention to the wording:
    It was cold enough for the electrons to join the plasma and form neutral atoms.
    So let's explain to me the difference between the hot plasma that existed before the universe cooled and the plasma that was created after it cooled.
    In short, there was no harm in the article being edited.
    The whole wording sounds like gpt chat gibberish.

  6. If "the universe went from a disorderly soup of high-energy particles to a more organized collection of galaxies and stars" then it went from a lower entropy level to a higher one, and something outside the physical system called the universe was needed to provide the universe with the energy needed for this transition? Do physicists have a plausible explanation for where this energy came from?

  7. The early galaxies are only detected because of a massive galaxy in the middle..
    That doesn't mean the beginning is there.

    They are weak because of the great distance and only the bright part is revealed
    This does not mean that these galaxies do not have arms that double their size, the arms are much weaker in the concentration of stars and certainly will not travel such a great distance.

    By the way, if the old galaxies are 13 billion years old..
    So this means that the Milky Way galaxy is already present 13 billion and was just waiting for this light to arrive..
    Otherwise, what preceded the matter in our galaxy to the matter that comes from 13 billion years ago?!

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