Scientists have used two large telescopes—one located on Earth and the other in space—to identify the presence of oxygen in the earliest known galaxy, which emits light approximately 300 million years after the Big Bang.
The galaxy, named JADES-GS-z14-0, was discovered by NASA’s James Webb Space Telescope in 2024. Recent observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile allowed two research teams to not only measure its significant distance accurately but also confirm the presence of oxygen signals.
This discovery, along with other emerging evidence, has dramatically impacted the scientific community by questioning previous beliefs that galaxies from this era—when the universe was merely two percent of its current 13.8 billion-year age—would lack many elements heavier than hydrogen and helium. Before the advent of the Webb telescope, other instruments like the Hubble Space Telescope and computer simulations posited that elements like oxygen, carbon, and nitrogen would not appear until 200 to 400 million years later.
Studies published in Astronomy & Astrophysics and The Astrophysical Journal propose that the distant galaxy contains about ten times more heavy elements than anticipated, prompting a reevaluation of how these early galaxies could have formed and evolved with such speed.
Prior to the introduction of the James Webb Space Telescope (JWST), researchers predominantly observed galaxies that were relatively "nearby," capturing an image of an evolved universe. Stefano Carniani from Scuola Normale Superiore in Italy, who led one of the studies, noted that assumptions about the early universe were based on such images, under the premise that this scenario was consistent throughout cosmic history.
The ancient galaxy JADES-GS-z14-0 is situated in the Fornax constellation. The images and data collected have led scientists to distinguish a variably chaotic gas flow in ancient galaxies like JADES-GS-z14-0, as opposed to the steady and continuous gas flows observed in present-day galaxies. This suggests that these early galaxies occasionally amassed large amounts of gas.
The prevailing theory posited that the first stars—known as "Population III stars"—formed when elements heavier than helium were scarce. These initial stars were considered massive, bright, and hot, ending their existence in supernovas that disseminated new chemical substances across space.
Heavy elements are created within the cores of stars and are disbursed into interstellar space when stars explode, potentially seeding the universe with these elements. However, it was believed that several star generations were needed before galaxies contained sufficient amounts of oxygen and other detectable heavy elements.
According to Sander Schouws from Leiden Observatory in the Netherlands, another lead author of the papers, very massive stars have relatively short lifespans—up to a few million years—which might explain the rapid proliferation of heavier elements in early galaxies.
The revelations from the Webb telescope indicate that many luminous galaxies existed during the cosmic dawn, a period 100 million to 1 billion years after the Big Bang. Some scientists suggest that galaxies from this era were able to form stars more efficiently, which left lesser amounts of excess gas and dust. If there were too much gas, it would dilute the heavy elements, making them less detectable. Other theories propose that intense starlight drove gas and dust outward, leading to brighter galaxies due to less material obscuring them. The possibility of supermassive black holes generating large jets potentially causing the brightness was considered, but studies of JADES-GS-z14-0 have yet to find any such evidence.
Images of JADES-GS-z14-0 have shown its brightness to be distributed over 1,600 light-years, indicating that young stars, rather than black hole emissions, dominate its light emission. If calculations are correct, the galaxy possesses a mass several hundred million times that of the sun.
Schouws highlights another consideration that might affect the interpretation of phenomena in this old galaxy: Bursty star formation could cause it to appear as though it is forming stars faster than it actually is. Bursty star formation results in galaxies becoming intermittently bright, potentially misleading scientists into perceiving rapid growth from a singular observation, whereas a longer-term average might tell a different story. In contrast to a steady star formation like that in the Milky Way, these galaxies may experience periods of rapid star creation followed by long stagnant phases.
The concept is that many stars of the same generation form and later die in supernovas nearly simultaneously. The gas is subsequently recycled into new stars, though this process remains irregular.
"This is a factor we need to consider," Schouws commented, "but it presents challenges."
