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Dwarf galaxies change knowledge about the Universe

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The James Webb Space Telescope (JWST) was used in conjunction with an effect predicted by Albert Einstein more than 100 years ago, enabling the discovery that small galaxies at the beginning of our Universe completely shaped it when it was less of a billion years.

The team responsible for the study found these galaxies, similar to dwarf galaxies that exist today, which played a vital role during a crucial stage in cosmic evolution that occurred between 500 million and 900 million years after the Big Bang, reports the Space.com.

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Such small galaxies also outnumbered other galaxies in the early Universe, according to the researchers, who added that it was likely that the kingdoms provided much of the energy needed for cosmic reionization, which was critical to the growth and progression of the Universe.

We are really talking about the global transformation of the entire Universe. The main surprise is that these small, faint galaxies had so much power that their cumulative radiation could transform the entire Universe.

Hakim Atek, main author of the research and astronomer at the Institut d'Astrophysique de Paris (France), in an interview with Space.com

Dwarf galaxies discovered by James Webb played a fundamental role in the Universe

  • Before about 380 million years after the Big Bang during the epoch of recombination, the Universe was opaque and dark;
  • This was due to the fact that, in its dense and superhot state, free electrons bounced endlessly around the particles of light, called photons;
  • Later, the Universe expanded and cooled enough to let electrons bond with protons and create the first atoms of hydrogen, the lightest and simplest element in the cosmos;
  • The disappearance of free electrons meant photons were suddenly released to travel, and as a result, the “dark era” of the Universe came to an end, causing the cosmos to come into the light;
  • The “first light” that appeared in the Universe can be seen today in the form of a cosmic fossil that uniformly fills the Universe called the “cosmic microwave background”, or CMB, for its acronym in English.

As electrons and protons have equal but opposite electrical charges, the first atoms were electrically neutral, but would soon undergo another transformation.

Evolution of the Universe with the end of the cosmic dark ages indicated (Image: NASA)

After 400 million years, the first stars and galaxies were formed, still in the era of reionization, in which neutral hydrogen, the predominant element in the Universe, became charged particles. Such particles are ions.

Ionization is caused by electrons absorbing photons and increasing their energy and breaking free from atoms. Until now, there was no information about where this ionizing radiation came from.

Suspected sources of radiation behind reionization included supermassive black holes that feed on gas from the accretion disks surrounding them (causing such regions to eject high-energy radiation), large galaxies with masses greater than billions of suns, and galaxies more small ones with masses lower than this.

We've been debating this question for decades, in fact, whether it's massive black holes or massive galaxies. There are even exotic explanations, such as the annihilation of dark matter that creates ionizing radiation. One of the best candidates was galaxies, and now we have shown that the contribution of small galaxies is enormous.

Hakim Atek, main author of the research and astronomer at the Institut d'Astrophysique de Paris (France), in an interview with Space.com

“We didn’t think that small galaxies would be so efficient at producing ionizing radiation. It is four times larger than we expected, even for normal-sized galaxies,” Atek continued.

Identifying dwarf galaxies with James Webb

Identifying smaller dwarf galaxies as the main sources of this ionizing radiation has long been a challenge, due to how faint they are.

“It was difficult to obtain this type of information and these observations, but the JWST has infrared spectroscopic capabilities. In fact, one of the reasons we built the JWST is to understand what happened during the epoch of reionization,” said researcher.

Even with JWST's impressive infrared observation power, detecting dwarf galaxies would not have been possible without a “help” from Albert Einstein. In this case, the 1915 theory of general relativity and the effect on light that it predicts.

General relativity suggests that all objects of mass deform the very fabric of space and time, which are actually united as a single entity, known as space-time.

Diagram shows how light from a background object is bent by a body in the foreground (Image: NASA, ESA and L. Calçada)

According to the theory, our perception of gravity arises as a result of this curvature. Furthermore, the greater the mass of an object, the more “extreme” the curvature of space-time. This way, the gravitational effects are stronger.

Curvature not only tells planets how to move in orbits around stars (and, in turn, tells stellar bodies how to orbit the supermassive black holes at the centers of their home galaxies), but it also changes the paths of light. what a coming from the stars.

Light from a background source can take other paths around a foreground object as it travels toward Earth, and the closer the path is to a mass object, the more it will be “bent.”

Therefore, light from the same object can reach Earth at different times as a result of the foreground object, or “lens”, as we can understand it.

Such a lens can change the location of the background object in the sky, or it can make the background object appear in multiple places in the same image in the sky. At other times, the light from the object in the background is amplified, consequently amplifying the object in the sky.

This effect is called “gravitational lensing,” used by JWST to great effect to observe ancient galaxies near the dawn of time that might otherwise have no chance of being seen.

How James Webb visualized dwarf galaxies

JWST used a galaxy cluster, called Abell 2744, as a gravitational lens to observe the recently studied distant and primitive dwarf galaxies and analyze the light emitted by them.

“Even for the JWST, these small galaxies are very faint, so we need to add gravitational lensing to amplify their outflow,” said Atek.

With the mystery of reionization apparently solved, at least in part, the team intends to expand the study on a larger scale with another JWST project, called GLIMPSE. They will try to confirm whether the location studied in the investigation is representative of the average distribution of galaxies in the Universe.

Next, in studying the reionization process, Atek and his colleagues will try to better understand the formation of the first galaxies, which, over 12 billion years, became the galaxies that exist today.

So far, we have mainly studied bright, massive galaxies, but they are not very typical of the early universe. So if we want to understand the formation of the first galaxies, we really need to understand the formation of tiny, low-mass galaxies. And that's what we'll try to do with this next program.

Hakim Atek, main author of the research and astronomer at the Institut d'Astrophysique de Paris (France), in an interview with Space.com

The study was published this Wednesday (28) in Nature.



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