Astronomers are making progress in their efforts to understand the origins of the first stars and galaxies that appeared in the universe, but they still have much to learn. Despite this, each new discovery brings them closer to unlocking the secrets of the cosmos.
Initial observations by the James Webb Space Telescope (JWST) suggest that the number of candidate galaxies in the early universe exceeds predictions, potentially requiring significant revisions to current cosmological models. The JWST, which began science operations in July and cost approximately $10 billion, is designed to study the faint infrared glow of the earliest luminous objects in the universe. Its capabilities allow it to observe the first few hundred million years after the big bang, providing more and better data on newborn galaxies than any other facility. So far, the JWST has discovered dozens of these galaxies, leading to speculation that the first galaxies may have formed earlier or shone brighter than previously thought, or that dark matter and dark energy may be more complex and mysterious than previously thought.
Scientists suspect that our understanding of cosmic history is incomplete due to the discovery of two early galaxies that have stood up to further scrutiny. The galaxies, which were discovered independently by two teams led by Rohan Naidu and Marco Castellano, are estimated to be 350 million and 450 million years old, respectively, making them the oldest known galaxies at the time of their discovery. Initially published on the preprint server arXiv.org, the two discovery papers have now undergone peer review and been published in the Astrophysical Journal Letters. There were concerns that the JWST’s instruments may have caused calibration issues, leading to inaccurate estimates of the distance to the galaxies. However, after thorough review, it has been determined that calibration is not an issue and the galaxies are “very robust candidates.” Further observations will be needed to confirm their record-breaking distances.
Astronomers have discovered several early galaxy candidates, some dating back as far as 200 million years after the Big Bang. Before the launch of the James Webb Space Telescope, it was unknown whether galaxies could form so early in the universe’s history, when matter was thought to be coalescing into the clumps necessary for the formation of large groups of stars. These discoveries have raised questions for theorists about the early stages of galaxy formation. “Do we really understand the early phases of the formation of these galaxies?” asked Garth Illingworth, an astronomer at the University of California, Santa Cruz, during a press conference held by NASA to announce the peer-reviewed validation of the first two candidates.
Dark matter, which does not interact through electromagnetic forces and is therefore only influenced by gravity, is believed to have played a key role in the formation of galaxies in the early universe. Shortly after the big bang, when the universe was still extremely hot, normal matter was unable to form large protogalactic clumps due to the high temperature. However, dark matter was able to immediately begin clumping together into large structures known as halos due to its reliance on gravity alone. These halos are thought to have acted as gravitational anchors for normal matter, allowing it to eventually coalesce and form galaxies. Even today, halos of dark matter continue to surround galaxies, influencing the movements of the stars within them.
Dark matter is a mysterious substance that does not interact with electromagnetic forces, only being affected by gravity. Scientists believe that it played a crucial role in the creation of galaxies in the early universe. After the big bang, the universe was very hot, preventing normal matter from coming together to form large protogalactic clumps. However, dark matter was able to form large structures called halos because it is only influenced by gravity. These halos are believed to have acted as gravitational anchors for normal matter, allowing it to eventually form galaxies. Even now, halos of dark matter can be found surrounding galaxies, influencing the movements of the stars within them.
It has been suggested that the halos in question may have been more effective at attracting regular matter and facilitating star formation. This theory suggests that these halos played a significant role in the early stages of star formation. According to research, the rate of star formation in the two candidate galaxies studied was at least 20 times higher than the current rate of star formation in our own galaxy, which is approximately one star per year. Another study suggests that Milky Way-sized galaxies may have formed just half a billion years after the Big Bang, which would require even higher rates of star formation. However, some experts have expressed skepticism about these high rates of star formation, stating that they may not be physically possible given the limitations of mass conversion into stars.
One possible explanation for the observation of bright, distant galaxies by the James Webb Space Telescope (JWST) is that stars in the early universe were more efficient at accumulating mass, resulting in larger and brighter stars. This idea is supported by the theory of Population III stars, which are believed to be the first stars in the universe and could have been hundreds of times larger than our sun. These stars, formed from primordial hydrogen and helium, would have had short lifespans of only a few million years, making them difficult to detect today. However, there is still some circumstantial evidence for their existence.
The James Webb Space Telescope (JWST) has discovered some distant galaxies that may contain evidence of Population III stars. These ancient stars would have been much hotter and brighter than the Population II and Population I stars that exist in the universe today, including our sun. To confirm the presence of Population III stars in these distant galaxies, the JWST will need to conduct spectroscopic analysis, which involves examining the spectrum of light emitted by the galaxy to determine the chemical elements present in its stars. According to cosmologist Daniel Whalen of the University of Portsmouth, a potential signature of Population III stars could be a particular spectral feature of helium that can only be produced by stars with temperatures above 100,000 degrees Celsius. If this feature is detected, it could indicate the existence of a massive Population III star.
The James Webb Space Telescope (JWST) may find that the rapid formation of massive galaxies in the early universe slowed down in later cosmic epochs. This could mean that the universe was expanding faster than current estimates suggest, potentially due to the influence of a particular type of dark energy called “phantom” models. These models allow for fluctuations in the potency of dark energy over time, and if they are accurate, it could mean that dark energy had a greater impact on the universe’s expansion shortly after the Big Bang than it does today. This finding would be in contrast with the commonly accepted Lambda Cold Dark Matter (Lambda-CDM) model, which incorporates current best estimates for the properties and effects of dark matter and dark energy on cosmic evolution.
Astronomers are still trying to understand the existence of numerous galaxy candidates in the early universe, and some of these ideas may seem unlikely, but they cannot be completely dismissed yet. It is possible that some of these galaxies may just be closer ones that appear more distant due to the presence of large amounts of dust, which also causes their light to appear redshifted. However, initial observations of one of the galaxies using the Atacama Large Millimeter/submillimeter Array in Chile did not provide much evidence for high levels of dust. The James Webb Space Telescope is the only instrument that can provide definitive answers about these galaxies, according to Castellano.
Further observations of galaxies like these may be conducted using the James Webb Space Telescope (JWST) in its first year of science, which runs until June 2023. Even more exciting results may be obtained in its second year of science, for which astronomers can now submit research proposals by January 27, 2023. According to Illingworth, “Spectroscopic follow-up with JWST is crucial and is likely to be a major focus of research on distant galaxies in Cycle 2.” The mystery of these bright objects remains unsolved, and it is important to determine their origins and understand what is causing them.
