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In a groundbreaking discovery, the James Webb Space Telescope (JWST) has revealed a treasure trove of over 800,000 galaxies lurking beyond the Milky Way. This monumental find, announced in June 2025, offers an unprecedented glimpse into the early universe.
Unlocking Cosmic Secrets in the COSMOS Field
The focus of this historic observation was the COSMOS field, a carefully selected region of the sky chosen for its lack of nearby stars and obscuring gases. This “slice of the universe,” though small at just 0.54 square degrees, provided the perfect window to peer into the cosmic past.
JWST’s exceptional ability to detect faint infrared light was crucial. Light from ancient galaxies stretches as it travels across the expanding universe, shifting into the infrared spectrum. Unlike telescopes like Hubble, JWST is specifically designed to capture this light, revealing galaxies previously hidden from view. The survey required a staggering 255 hours of continuous observation, but the payoff was immense.
COSMOS-Web: A Universe Unveiled
The result of this dedicated effort is COSMOS-Web, the largest and most detailed map of the universe ever created. This dataset contains over 800,000 galaxies, stretching back an astonishing 13.5 billion years – 98% of the universe’s history! It’s like looking back in time to when the universe was only 300 million years old.
Beyond the sheer number of galaxies, scientists were astonished by their density in the early universe. The first 500 million years after the Big Bang contained ten times more galaxies than previously predicted.
Professor Casey notes, “We’re also seeing supermassive black holes that aren’t even visible with Hubble. And they’re not just seeing more, they’re seeing different types of galaxies and black holes.”
Democratizing Access to the Universe
Perhaps the most exciting aspect of this discovery is its accessibility. Unlike many large-scale astronomical surveys, the COSMOS-Web data is publicly available. After two years of processing, the entire database is now open to anyone, from undergraduate students to independent researchers.
This democratization of data empowers a new generation of astronomers to explore the early universe, unraveling its mysteries and deepening our understanding of the cosmos. With COSMOS-Web, the secrets of the universe are now within reach, paving the way for further discoveries about the universe’s origins and evolution.
Credits: M. Franco / C. Casey / COSMOS-Web collaboration