Back to the Future's 30th anniversary has resulted in many speculations about the modern technology the film was able to predict. The discovery of 252 dwarf galaxies couldn't have had a better timing, just like Doc Brown and Marty McFly, it enabled astronomers to look back into the past to see how the early universe was formed, approximately 600 to 900 million years after the Big Bang.

The discovery was published in the Astrophysical Journal where the researchers described how the light discharged by these dwarf galaxies played a role in the epoch of reionization. This is a period of time in the early universe when the dense hydrogen gas that covered the universe started to dissolve and when ultraviolet light began to travel to distant areas without being blocked by the hydrogen fog.

In the paper, the research team led by Hakim Atek, described that the dwarf galaxies were crucial in keeping the universe clear. The researchers also explained that the reionization period concluded 700 million years after the Big Bang

Era of Recombination

People know about the Big Bang Theory, basically it's how the universe was born. Simply put, the theory explains how the universe started as a small singularity and expanded to what we know now as the 13.8-billion-years-old universe. But the universe we know today didn't look this way during its early years.

The period following the Big Bang is called the Dark Ages. It was a very dark place with no stars, planets or galaxies. The universe was like a hot boiling soup of electrons, neutrons, protons and other particles. The neutrons and protons combined to form ionized atoms of deuterium and hydrogen. The ionized atom deuterium combined again with helium-4. These two ionized atoms - helium and hydrogen - fused with electrons that transformed them into neutral atoms. At this point in time, the universe was made of helium, hydrogen and small traces of other light elements. Among these elements, hydrogen was abundant.

This fusion of particles is called "Recombination", which took place 400,000 years after the big explosion. This period in the universe signaled the end of the Dark Ages. Prior to this era, light could not travel freely because it would throw off free electrons. However, since the free electrons partnered with protons, light was able to travel freely.

The once opaque universe became transparent. The Era of Recombination is the earliest point in the universe's history where scientists can analyze using any form of light. Using satellites like the Wilkinson Microwave Anisotropy Probe (WMAP) and the Cosmic Microwave Background Explorer (COBE), scientists determine the Cosmic Microwave Background (CMB), the amount of radiation that covers the universe. These are traces of thermal radiation dating back to the Era of Recombination.

Era of Reionization

Another important era in the cosmos' history occurred after the birth of the first stars. Scientists believe that the earliest stars are 30 to 300 times bigger than the Sun. They also believe that the early stars burned millions of times brighter than the Sun for several million years before exploding into what is called a supernova.

At first, the stars' ultraviolet light broke the hydrogen atoms into protons and electrons. This process is called ionization and scientists suggest that this phase started when the universe was nearly one billion years old.

This point in the history of the cosmos is called the Era of Reionization when neutral hydrogen was 'reionized' by the radiation of the first stars. By understanding the earliest sources of light, scientists can determine how they greatly influenced the formation of galaxies.

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