Astronomers unveil hidden structures of first galaxies 13 billion years ago using ALMA’s cosmic time machine
By willowt // 2025-07-14
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  • Researchers used the ALMA telescope to map 39 early galaxies at 1 billion years post-Big Bang, revealing rotating disks and clumpy star formation.
  • Two extraordinary galaxies—CRISTAL-13 (dust-shrouded) and CRISTAL-10 (unusually faint carbon emissions)—hint at cosmic extremes.
  • ALMA’s [CII] emission data exposes cold gas and star formation, challenging previous galaxy evolution models.
  • Collaboration with Hubble and JWST provides multi-wavelength insights into galactic evolution.
  • Findings bridge gaps in understanding how proto-spiral galaxies like the Milky Way formed.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of astronomers has unveiled the first detailed maps of galaxies that existed just 1 billion years after the Big Bang. Published in Astronomy & Astrophysics, the CRISTAL survey analyzed 39 representative star-forming galaxies from the infancy of the 13.8 billion-year-old universe, revealing their internal structure through ALMA’s unprecedented sensitivity. This breakthrough, combining with infrared data from the James Webb and Hubble Space Telescopes, peels back cosmic history to examine how galaxies transitioned from chaotic birthplaces of stars into ordered systems like the Milky Way.

Galactic time machine: How ALMA peers into the past

ALMA’s ability to detect [CII] emission—light from ionized carbon atoms in cold interstellar gas—allowed researchers to trace the hidden architecture of early galaxies. These galaxies, once visible only as faint smudges, now come alive as “complex ecosystems,” according to co-author Loreto Barcos-Muñoz of NRAO. The [CII] maps showed star formation occurring in colossal clumps spanning thousands of light-years and revealed rotating gas disks, suggesting proto-spiral structures. Such disks are precursors to modern galaxies like the Milky Way, offering clues to their evolutionary pathways. “Thanks to ALMA’s unique sensitivity, we can resolve these galaxies like never before,” said study leader Rodrigo Herrera-Camus. “CRISTAL is showing us how gas shaped the galaxies we see today.”

Mysterious monsters and the dust of creation

Two galaxies in the survey stood out as enigmas. CRISTAL-13, shrouded in dense dust, hid newborn stars until ALMA detected their reprocessed infrared glow. This “monster” galaxy’s structure would remain invisible to visible-light telescopes like Hubble. Meanwhile, CRISTAL-10 defied expectations with faint ionized carbon emissions, a trait seen in local obscured galaxies like Arp 220. Its weak [CII] signal hints at extreme physical conditions—perhaps supermassive black holes or energetic outflows altering its interstellar medium. “These observations highlight ALMA’s potential as a time machine,” said ALMA’s Sergio Martín. “They let us peer into the early universe’s most extreme environments.”

Bridging the gap: Why this matters for modern astronomy

Until now, prevailing models underestimated the diversity and internal complexity of early galaxies. CRISTAL’s findings force a reevaluation: galaxies formed stars faster and in more turbulent conditions than simulations predicted. The survey also sets the stage for follow-up studies with JWST, which will continue probing dust-enshrouded regions to clarify how gas fuels star formation and whether mergers or internal dynamics drive disk formation. “As we challenge old paradigms, we open doors to new theories,” said Herrera-Camus. “This is a major step toward understanding how galaxies like the Milky Way came to be.”

The future is in cosmic time travel

CRISTAL’s success underscores the synergy between ground-based and space telescopes. ALMA’s focus on cold gas complements JWST’s infrared stellar imaging, creating a multi-dimensional picture of galactic evolution. Future Large Programs at ALMA will expand this project to uncover how these “infant” galaxies matured over cosmic time. The universe’s first billion years remain a puzzle, but with tools like ALMA, humanity’s curiosity is poised to unravel its mysteries—one time machine image at a time.

A new epoch for cosmic archaeology

From its perch in Chile’s Atacama Desert, ALMA has gifted astronomers with a time-transporting toolkit to decode cosmic origins. The CRISTAL survey doesn’t just map galaxies—it rewrites our cosmic story. As telescopes like JWST join this quest, the boundary between the known and unknown dissolves, inviting scientists to explore ever deeper into the universe’s unfolding tale. In the words of Herrera-Camus, CRISTAL “shows us how the first galaxies’ gas and stars built the cosmos we inhabit today.” The adventure, quite literally, is only just beginning. Sources for this article include: LiveScience.com AlmaObservatory.com RudeBaguette.com
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