Brightest era of the universe reveals how the Milky Way formed

A recent deep look into the universe has captured a rare moment when certain young galaxies ignited their very first major burst of stars. By watching this cosmic flashback, astronomers have pinpointed the era when structures much like the Milky Way formed and began to shine.

The discovery opens a new window into how galaxies grow from faint clouds into the grand spirals that fill today’s skies.

Researchers from Rutgers University–New Brunswick, working with partners across multiple institutions, analyzed a remarkable class of ancient objects called Lyman Alpha Emitters (LAEs). These objects sit roughly 12 billion light-years away during the period known as Cosmic Noon.

The team combined specialized images from the ODIN survey – captured with the Dark Energy Camera in Chile – with machine-learning tools to sift out key details of each galaxy’s life story.

Galaxies blaze with young stars

LAEs blaze because young, hot stars flood them with ultraviolet radiation. As the universe stretches, that radiation lengthens into visible Lyman alpha light, turning every LAE into a beacon that modern telescopes can see.

“LAEs have been identified as progenitors of typical present-day galaxies like our own Milky Way,” said lead author Nicole Firestone, a research fellow at Rutgers.

“Now that we know when they first formed their stars, we have discovered our own galaxy’s ‘origin story,’ unlocking one of the mysteries of creation.”

A starting point for galaxies

The project builds on earlier work led by Professor Eric Gawiser, who showed that LAEs should mature into galaxies resembling the Milky Way.

Yet one puzzle lingered: Did astronomers need to look even farther back to see those systems take their first breath?

“Until now, it remained an open question whether we had looked far enough back in time to find the starting points for the Milky Way and galaxies like it,” Gawiser said. “Now we know the answer to that question is yes.”

Decoding cosmic light with AI

To reach that verdict, the scientists drew on ODIN’s narrow-band views, covering one hundred square degrees of southern sky. LAEs pop out in those frames because they appear far brighter in a single narrow wavelength than in ordinary colors visible to human eyes.

The team then applied an algorithm – created at Rutgers by Gawiser and former student Kartheik Iyer – that reconstructs how quickly each galaxy has forged stars through time.

“For the very first time, we have been able to definitively show that most LAEs are experiencing their first major starburst at the time of observation and only have very young stars,” Firestone said.

Earliest stages of the Milky Way

Cosmic Noon spans roughly two to three billion years after the Big Bang, when galaxy building hit top speed.

By targeting this era, the researchers caught LAEs at the exact moment gas collapsed into their first stellar generations.

The analysis indicates that ninety-five percent of the sample sits at peak production, rapidly turning raw hydrogen into newborn stars. That timing implies the Milky Way formed and lit up during the same interval, offering a direct glimpse of its earliest stages.

How galaxies first formed

Knowing that LAEs are genuine youngsters answers a fundamental problem in cosmic evolution. If the galaxies had been older systems reigniting, their light would tell a very different story about how spiral disks assemble and how long star-forming gas can linger.

By confirming their youth, the study narrows down theories on how galaxies collect matter, how fast they grow, and how soon they settle into well-defined shapes.

“This discovery helps us understand what our own Milky Way galaxy looked like when it first started forming stars,” Gawiser said.

A map for future telescopes

The Rutgers results arrive just as the James Webb Space Telescope begins to spot even fainter LAEs farther back in time.

Webb’s infrared vision will extend the family tree, linking these Cosmic Noon beacons to dimmer conditions from an even earlier dawn.

By comparing star-formation rates across those epochs, astronomers hope to trace the entire arc from the universe’s first sparks to the structured spiral arms we see overhead now.

Expanding the star catalog

Beyond Webb, upcoming surveys with ground-based giants such as the Vera C. Rubin Observatory promise to add color, motion, and chemical fingerprints to the LAE story.

Each new dataset will refine models of how gas cools, how metals enrich fresh generations of stars, and how small galaxies merge into larger ones.

Machine learning methods similar to those pioneered by the Rutgers group will be essential for sorting through the torrent of observations.

Tomorrow’s view of the cosmos

For the moment, the study marks a milestone. By catching LAEs in their first blaze of activity, researchers have identified the era when galaxies like the Milky Way formed and began to sparkle.

That single insight reshapes timelines for galaxy evolution, sets tighter constraints on cosmological models, and gives scientists a touchstone for future exploration.

As instruments grow sharper and computer tools grow smarter, the faint glimmers of Cosmic Noon will continue to illuminate the universe’s earliest chapters, guiding us toward a fuller account of how every star, planet, and patch of sky first came to be.

The study is published in The Astrophysical Journal Letters.

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