The faintist early-universe galaxy was born 13 billion years ago immediately after the formation of the universe. The detected galaxy could help scientists understand the "reionization epoch" when first stars became visible.
Astronomers have spotted the faintest and furthest galaxy yet. The galaxy came into existence just after the Big Bang or 13 billion years ago when the universe was a toddler in cosmic terms.
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The detection of the faintest early-universe galaxy was made possible through powerful telescope at W.M. Keck Observatory on Mauna kea Hawaii.
“The galaxy is exciting because the team infers a very low stellar mass, or only one percent of one percent of the Milky Way galaxy,” said Marc Kassis, staff astronomer at Keck Observatory. “It's a very, very small galaxy and at such a great distance, it’s a clue in answering one of the fundamental questions astronomy is trying to understand: What is causing the hydrogen gas at the very beginning of the Universe to go from neutral to ionized about 13 billion years ago. That's when stars turned on and matter became more complex.”
Researchers caught the glimpses of faint, distant galaxy thanks to a cluster of larger galaxies MACS2129.4-074, which acted like a giant magnifying glass. The phenomenon is called gravitational lensing and was predicted by Einstein in which an object in this case the faint galaxy is magnified by the gravity of another massive object that is lying between it and the observer. These massive objects are capable of bending the light from the source as it travels and makes it visible to observer.
“If the light from this galaxy was not magnified by factors of 11, five and two, we would not have been able to see it,” said lead researcher Kuang-Han Huang from University of California, Davis. “It lies near the end of reionization epoch, during which most of the hydrogen gas between galaxies transitioned from being mostly neutral to being mostly ionized. That shows how gravitational lensing is important for understanding the faint galaxy population that dominates the reionization photon production.”
Reionization epoch is a period in the history of early universe when neutral intergalactic material underwent ionization and lit up luminous sources like stars, galaxies or quasars for the first time.
“We now have good constraints on when the reionization process ends – at redshift around 6 or 12.5 billion years ago – but we don’t yet know a lot of details about how it happened,” said Huang. “The galaxy detected in our work is likely a member of the faint galaxy population that drives the reionization process.”
The cluster of galaxies MACS2129.4-0741which was hanging in front of detected galaxy was large enough to magnify the light of the galaxy and to create different images of it. The galaxie’s magnified images were seen by both Keck Observatory and Hubble Space Telescope, confirming they were exactly the same and represent a single object.
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“Keck Observatory’s telescopes are simply best in the world for this work,” said Marusa Bradac of the University of California. “Their power, paired with the gravitational force of a massive cluster of galaxies, allows us to truly see where no human has seen before.”