We finally know what brought light to the darkness and formless void of the early universe.
According to the Hubbles and James Webb Space Telescope, the origin of free-flying photons at the dawn of the universe was in dwarf galaxies, which erupted with life and cleared the murky hydrogen haze that filled intergalactic space.
Astrophysicist Iryna Chemerynska of the Institut des Astrophyses in Paris said: "This discovery reveals the key role played by ultra-faint galaxies in the evolution of the early universe. ”。
They produce ionized photons that convert neutral hydrogen into ionized plasma during cosmic reionization. This highlights the importance of understanding low-mass galaxies in shaping the history of the universe. ”
At the beginning of the universe, within a few minutes of the universe's greatness, space was filled with a dense fog of high temperatures of ionized plasma. Not even the faint light will penetrate the fog; Photons simply scatter free electrons floating around, effectively darkening the universe.
About 300,000 years later, as the universe cools, protons and electrons begin to clump together to form a neutral hydrogen (and a little bit of helium) gas. Most wavelengths of light can penetrate this neutral medium, but there are very few light sources that produce it. But from this hydrogen and helium, the first stars were born.
The first stars emit radiation strong enough to strip electrons from their nuclei and reionize the gas. However, by now, the universe has expanded to the point where gas is diffuse, unable to stop the rays of light. About 1 billion years later, the end of the so-called dawn period of the universe, the universe was completely reionized. Greatly! The lights are on.
But because there is so much darkness in the dawn of the universe, and because it is so dim and distant in time and space, it is difficult for us to see what is there. Scientists believe that the ** responsible for most of the cleanup must be powerful — for example, huge black holes, whose accretion produces red-hot light, and large galaxies in the throes of star formation (newborn stars produce a lot of ultraviolet light).
JWST was designed in part to peek into the dawn of the universe and try to see what lurks within. It was very successful, revealing various surprises at this critical moment in the formation of the universe. Surprisingly, telescope observations suggest that dwarf galaxies are key to reionization.
JWST deepfield images, some of which were identified by the researchers as drivers of reionization. (Hakeem Artek, Sorbonne University, JWST).
An international team led by astrophysicist Hakeem Artek at the Institut des Astrophysics in Paris studied JWST data called the Abell 2744 galaxy cluster, supported by Hubble data. Abel-2744 is so dense that space-time distorts around it, forming a cosmic lens; Any distant light that travels through time and space to us is amplified. This allows researchers to see tiny dwarf galaxies close to the dawn of the universe.
They then used JWST to obtain detailed spectra of these tiny galaxies. Their analysis showed that these dwarf galaxies were not only the most abundant types of galaxies in the early universe, but also much brighter than expected. In fact, the team's research shows that there are 100 more dwarf galaxies than large galaxies, and their total output is four times the ionizing radiation commonly assumed for large galaxies.
"Together, these space power plants emit enough energy to complete the mission," Atek said. ”。Despite their small size, these low-mass galaxies are prolific producers of high-energy radiation, and during this period, their abundance is so great that their collective impact can alter the state of the entire universe. ”
This is the best evidence of the forces behind reionization, but there is more work to be done. The researchers looked at a small patch of the sky; They needed to make sure that their sample was not just an anomalous cluster of dwarf galaxies, but a representative sample of the entire cluster of galaxies at the dawn of the universe.
They intend to study more cosmic lensed regions in the sky to get a wider sample of early galaxy populations. But on this one sample alone, the results are incredibly exciting. Ever since we knew about reionization, scientists have been searching for an answer to it. We are on the verge of finally dispelling the fog.
Themiya Nanayakkara, an astrophysicist at Swinburn University of Technology in Australia, said: "We have now entered uncharted territory in JWST. ”。
This work raises more exciting questions that we need to answer in the process of mapping the evolutionary history of our origins. ”