Scientists have discovered that tiny galaxies in the early cosmos packed a big punch, altering the entire universe when it was less than 1 billion years old. They have done this by using the James Webb Space Telescope (JWST) and an effect that Albert Einstein predicted over a century ago.
The multinational group discovered that the galaxies, which resemble modern dwarf galaxies, were essential to cosmic evolution between 500 and 900 million years after the Big Bang. The scientists note that in the early cosmos, the number of these little galaxies far surpassed that of larger ones. They also speculate that the majority of the energy required for a process known as cosmic reionization was probably provided by these worlds. Cosmic reionization played a crucial role in the universe’s development.
“We’re really talking about the global transformation of the entire universe,” Hakim Atek, research lead author and an astronomer at the Institut d’Astrophysique de Paris, told. “The main surprise is that these small, faint galaxies had so much power, their cumulative radiation could transform the entire universe.”
Minor Motivators for Significant Transformations
The now 13.8 billion-year-old universe was opaque and dark before 380 million years after the Big Bang, a time known as the epoch of recombination. This happened due to free electrons’ constant bouncing around photons, which are light particles, in its dense and extremely hot condition.
However, the universe had later expanded and cooled enough during the recombination era to enable electrons to combine with protons to form the first hydrogen atoms, the lightest and most basic element in the universe. The “dark age” of the cosmos came to an end when unbound electrons vanished, allowing photons to instantly travel at will. Suddenly the universe was illuminated by light. Today, this “first light” is visible as the “cosmic microwave background,” or “CMB,” a cosmic fossil that evenly permeates the cosmos.
These initial atoms were electrically neutral since protons and electrons had equal but opposing electric charges, but they would shortly go through another change.
Following the formation of the first stars and galaxies 400 million years later, neutral hydrogen—the most common element in the universe at the time—became charged particles during the reionization period. We refer to these particles as ions. When electrons absorb photons and increase their energy, they break free from atoms and generate ionization. Scientists were unsure about the source of this ionizing radiation until recently.
Supermassive black holes that feed on gas from the accretion disks around them, causing these regions to eject high-energy radiation, large galaxies with masses greater than one billion suns, and smaller galaxies with masses less than this were suspected to be the source of radiation behind reionization.
“We’ve been debating this issue for decades, actually, whether it’s massive black holes or massive galaxies. There are even exotic explanations, like dark matter annihilation that creates ionizing radiation,” Atek said, “One of the best candidates was galaxies, and now we’ve shown that the contribution of small galaxies is huge.
“We didn’t think small galaxies would be so efficient at producing ionizing radiation. It’s four times higher than what we expected, even for normal-sized galaxies.”
Since smaller dwarf galaxies are so weak, it has long been difficult to identify them as the primary producers of this ionizing radiation.
“It was hard to get this kind of information and these observations, but the JWST has spectroscopic capabilities in the infrared. In fact, one of the reasons we built the JWST is to understand what happened during the epoch of reionization,” Arek said.
Albert Einstein’s 1915 theory of general relativity and the predicted influence on light it has would not have allowed for the detection of these dwarf galaxies, even with the powerful infrared observation capability of the JWST.
An Assistive Gesture from Albert Einstein
According to general relativity, all mass-producing things distort space and time, which are actually one unique entity known as “spacetime.” According to the hypothesis, it is this curvature that gives rise to our feeling of gravity. The curvature of spacetime becomes more “extreme” with increasing object mass. Consequently, the greater its gravitational pull.
This curvature not only modifies the pathways taken by light emanating from the stars, but it also instructs planets on how to orbit their parent stars and, in turn, those stellar bodies on how to orbit the supermassive black holes in the centers of their own galaxies.
As light from a background source moves toward Earth, it might follow many routes around a foreground item; the more “bent” the light becomes, the closer the path comes to an object with a large mass. The foreground, or “lensing,” object causes light from the same object to arrive at Earth at various times.
This lensing has the ability to move the backdrop object’s position in the sky or make it appear more than once in the same sky image. At other times, the item in the backdrop appears larger in the sky due to the enhanced light from that object.
The JWST has been making excellent use of this phenomenon, termed as “gravitational lensing,” to see old galaxies close to the beginning of time that it would not have been able to detect otherwise.
The JWST used the galaxy cluster Abell 2744 as a gravitational lens to observe and study the recently discovered distant and early dwarf galaxies. “Even for the JWST, these small galaxies are very faint, so we needed to add gravitational lensing to amplify the flux of from them,” Atek stated.
Now that the enigma around reionization may have been resolved, the group hopes to expand this investigation to a broader scale with the JWST project GLIMPSE. First, the researchers will attempt to verify that the specific site under study is indicative of the universe’s average distribution of galaxies.
Then, Atek and associates will work to gain a deeper understanding of the development of the first galaxies, which evolved into modern galaxies over a period of 12 billion years, in addition to researching the reionization process.
“So far, we’ve been really studying mostly bright, massive galaxies, but they are not very typical in the early universe,” Atek concluded. “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 this is what we will be trying to do with this upcoming program.”