Astronomers used the James Webb Space Telescope (JWST) and estimated this effect Albert Einstein More than 100 years ago, we discovered that small galaxies in the early universe had a massive impact that shaped the entire universe when it was less than 1 billion years old.
The international team found that galaxies similar to the dwarf galaxies that exist today played a vital role in a crucial phase of cosmic evolution that occurred between 500 and 900 million years after the Big Bang. These smaller galaxies also far outnumber larger galaxies in the baby universe, the scientists say, adding that these realms likely provide most of the energy needed for a process called cosmic reionization. Cosmic reionization was critical to the growth and progress of the universe.
“We’re actually talking about a global transformation of the entire universe,” study lead author Hakim Atek, an astronomer at the Institut d’Astrophysique de Paris, told Space.com. “The real surprise was that these small, faint galaxies had so much power that their cumulative radiation could transform the entire universe.”
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Small drivers behind big changes
About 380 million years before the Big Bang, during a period called the recombination age, the universe, now 13.8 billion years old, was opaque and dark. This was because free electrons, in a dense and extremely hot state, bounced endlessly around particles of light called photons.
But later, in the age of recombination, the universe expanded and cooled enough to allow electrons to bond with protons and create the first atoms of hydrogen, the lightest and simplest element in the universe. This disappearance of free electrons meant that photons could suddenly travel freely, resulting in the end of the “dark age” of the universe. The cosmos suddenly became transparent to light. This “first light” can be seen today in the form of a cosmic fossil that evenly fills the universe, called the “cosmic microwave background” or “CMB”.
Because electrons and protons have equal but opposite electrical charges, these first atoms were electrically neutral, but they would soon undergo yet another transformation.
After 400 million years, the first stars and galaxies formed, then in the age of reionization, neutral hydrogen, the dominant element in the universe, decayed into charged particles. These particles are called ions. Ionization occurs when electrons absorb photons and break away from atoms by increasing their energy. Until now, scientists weren’t sure where this ionizing radiation was coming from.
Suspects for the radiation source behind reionization include supermassive black holes, which feed on gas from surrounding accretion disks, causing these regions to emit high-energy radiation; large galaxies with masses greater than 1 billion Suns; and smaller galaxies with masses less than that. It was located. .
“Actually, we have been discussing this issue for decades about whether there are large black holes or large galaxies. There are even exotic explanations such as the destruction of dark matter, which creates ionizing radiation,” Atek said. “One of the best candidates was galaxies, and now we have shown that the contribution of small galaxies is very large.
“We didn’t think small galaxies would be this effective at producing ionizing radiation. This is four times higher than we expected even for normal-sized galaxies.”
Determining that smaller dwarf galaxies are the main sources of this ionizing radiation was a difficult task for a long time because they are so faint.
“It was difficult to obtain this kind of information and these observations, but JWST has spectroscopic capabilities in the infrared. In fact, one of the reasons we built JWST is to understand what is happening in the reionization era,” Arek said.
Even with JWST’s impressive infrared observing power, detecting these dwarf galaxies would not have been possible without the help of Albert Einstein, more specifically his 1915 theory of general relativity and the impact it predicted on light.
Helping hand from Albert Einstein
General relativity proposes that all objects with mass distort the fabric of space and time, and that they actually merge into a single entity called “spacetime.” According to the theory, our perception of gravity arises as a result of this curvature. The greater the mass of an object, the more “extreme” the curvature of spacetime. Therefore, the stronger the gravitational effects.
This curvature not only tells planets how to move in orbits around stars and stellar bodies how to orbit supermassive black holes at the centers of their galaxies, but also changes the paths of light from stars.
Light from a background source can take different paths around a foreground object as it travels towards Earth, and the closer that path is to a massive object, the more it “bends”. Thus, light from the same object can reach the Earth at different times as a result of the foreground, or “lensing” object.
This lensing can change the position of the background object in the sky or cause the background object to appear in more than one place in the same sky image. Other times, the light from the background object is amplified, thus magnifying that object in the sky.
This effect is known as “gravitational lensing,” and JWST uses it to great effect to observe ancient galaxies near the beginning of time that we would otherwise have no chance of seeing.
To observe the newly studied distant and early dwarf galaxies and analyze the light they emit, JWST used a galaxy cluster called Abell 2744 as a gravitational lens. “Even for JWST, these small galaxies are too faint, so we needed to add gravitational lenses to strengthen the flow from them,” Atek said. said.
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With the reionization mystery potentially solved, the team now aims to extend this work to a larger scale with another JWST project called GLIMPSE. Researchers will first try to verify that the particular location examined in this research represents the average distribution of galaxies in the universe.
Beyond examining the reionization process, Atek and his colleagues will then aim to better understand the formation of the first galaxies that grew over 12 billion years into today’s galaxies.
“So far we have mostly studied bright, massive galaxies, but these are not very typical in the early universe,” Atek concluded. “So if we want to understand the formation of the first galaxies, we need to understand the formation of really small, low-mass galaxies. And that’s what we’ll try to do with the upcoming program.”
The team’s research was published in the journal Nature on Wednesday, February 28.