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An image of the massive galaxy cluster MACS J0416 with a three-color composite image of LAP1-B in “velocity space” (inset).(Image credit: NASA/ESA/CSA/K. Nakajima et al. (2026))Share this article 0Join the conversationFollow usAdd us as a preferred source on GoogleSubscribe to our newsletter
A paramount accomplishment of the James Webb Space Telescope is its ability to expand the frontiers of astronomy by enabling the observation of galaxies that existed in the nascent universe, less than a billion years following the Big Bang. This epoch, referred to as the Epoch of Reionization, corresponds to what celestial scientists have affectionately termed the “Cosmic Dark Ages.” During this period, spanning from 380,000 to 1 billion years post-Big Bang, the cosmos was saturated with neutral hydrogen, and any luminous sources visible today are so dramatically redshifted that they lie beyond the detection capabilities of conventional telescopes.
Leveraging Webb’s sophisticated infrared instrumentation and spectrometers, researchers can now penetrate this obscuring veil and examine the evolution of galaxies since the earliest cosmological eras. In a recent revelation, an international consortium of astronomers utilized Webb, along with the technique of gravitational lensing, to obtain a rare glimpse of LAP1-B, an exceedingly faint galaxy dating back to 800 million years after the Big Bang. Employing Webb’s spectrometers, the team successfully characterized this galaxy, confirming it as the most metal-poor galaxy observed in the early Universe to date.
The research endeavor was spearheaded by Associate Professor Kimihiko Nakajima of Kanazawa University. The scientific paper detailing their findings was published on May 13th in the esteemed journal Nature.
In the immediate aftermath of the Big Bang, the universe was composed solely of light elements like hydrogen and helium; the elements essential for life, such as carbon and oxygen, were absent. These heavier elements were synthesized within the cores of the very first generation of stars, known as Population III stars, and subsequently dispersed when these stars underwent supernova explosions, ejecting their outer envelopes. For many years, astronomers have aspired to discover these primordial stars to observe the genesis of heavier elements seeding the cosmos. This pursuit has been challenging because the earliest galaxies that harbored Population III stars appear remarkably small and dim.
A timeline illustrating the universe’s progression subsequent to the Big Bang.
Consequently, analyzing their elemental composition via spectroscopy was presumed virtually unfeasible until the present. Nakajima’s research builds upon the initial detection of LAP1-B by incorporating JWST spectral data, revealing an unprecedentedly low oxygen abundance, specifically 1/240th of the sun’s level. When this is considered alongside an elevated carbon-to-oxygen ratio and a dominant dark matter halo, these findings strongly suggest that LAP1-B is a precursor to the fossil galaxies discovered in proximity to the Milky Way. Astronomers have been actively seeking these “ancestor” galaxies, positioning LAP1-B as a historically significant window into the earliest phases of galactic formation.
Typically, we function as ‘cosmic archaeologists,’ attempting to reconstruct the past by examining ancient stars in our vicinity. However, we are now capable of directly analyzing the gas from the original scene, dating back 13 billion years.”
Kimihiko Nakajima, associate professor at Kanazawa University
The research team benefited from the presence of an intervening galaxy cluster, which served as a gravitational lens, amplifying the light originating from LAP1-B by a factor of 100. Following 30 hours of observation and meticulous deep spectroscopy, the team finally succeeded in delineating the chemical composition of this galaxy. Beyond its chemically primitive nature, the galaxy’s carbon-to-oxygen ratio closely aligns with theoretical projections for the material dispersed by Population III star explosions.
Associate Professor Nakajima stated in a press release from Kanazawa University: “I was immediately exhilarated by the profound scarcity of oxygen indicated by the data. Discovering a galaxy in such a rudimentary state is remarkable. It presents a chemical fingerprint that unequivocally points to a primordial galaxy captured in the moments shortly after its genesis.”
The team also ascertained that LAP1-B possesses exceptionally low mass (under 3,300 Solar masses), implying that the majority of the galaxy comprises dark matter in the form of a halo.
In conjunction with its distinctive chemical makeup, this characteristic makes it an almost perfect analogue to the “Ultra-Faint Dwarf galaxies (UFDs)” observed near the Milky Way today. Professor Masami Ouchi (NAOJ/University of Tokyo), a member of the research collective, remarked: “UFDs are not only the faintest galaxies; they consist of ancient stars exceeding 12 billion years in age and are often characterized as ‘fossils of the universe.’ Astrophysicists hypothesized they might be remnants of the universe’s earliest galaxies due to their lack of heavy elements, but a direct connection had never been established – until we identified LAP1-B. It is a surprising revelation that LAP1-B precisely matches the ‘ancestor’ we had only theorized. This discovery aids in resolving the enigma of how these cosmic relics have persisted in their present form up to this point in time.”
Galaxy Evolution: James Webb Space Telescope Science – YouTube
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The collective findings offer astronomers a novel methodology for charting the genesis of heavier elements within the Universe and the formation of its most ancient structures. The subsequent phase will involve the team utilizing JWST data to seek out even more chemically primordial objects, including those that formed first.
As Nakajima elaborated: “We aspire for this discovery to signify a momentous stride in comprehending how the elements that constitute our own beings were initially created and accumulated throughout the Universe.”
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