Key Takeaways:

  1. Serendipitous discovery: Astronomers stumbled upon two hidden galaxies at the edge of the universe while studying brighter neighboring galaxies.
  2. Ancient origins: These obscured galaxies formed over 13 billion years ago, shedding light on cosmic dawn, the era when the first stars and galaxies emerged.
  3. Thick dust veil: The galaxies, named REBELS-12-2 and REBELS-29-2, were concealed behind thick clouds of cosmic dust and remained invisible in UV and optical light.
  4. ALMA’s role: The Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, with its sensitivity to far-infrared wavelengths, enabled the detection of these hidden cosmic objects.
  5. Implications for research: The discovery suggests that up to one in five galaxies from the cosmic dawn era may be concealed by cosmic dust, highlighting the need for deeper and wider surveys.

In a twist of fate, astronomers have stumbled upon a remarkable celestial find: two hidden galaxies situated at the far reaches of the cosmos, shrouded behind a dense curtain of interstellar dust. These enigmatic galaxies came into existence more than 13 billion years ago, a mere 800 million years following the birth of the universe itself. Their discovery holds the promise of aiding scientists in locating other ancient cosmic artifacts concealed by cosmic dust.

This serendipitous revelation unfolded under the guidance of Yoshinobu Fudamoto, an astronomer affiliated with the Research Institute for Science and Engineering at Waseda University, Japan, and the National Astronomical Observatory of Japan (NAOJ). While conducting a study of neighboring galaxies emitting intense ultraviolet (UV) light, Fudamoto’s team chanced upon eerie spectral signals emanating from these two hidden galaxies.

The unexpected discovery of these galaxies lurking at the universe’s edge underscores a critical insight: our existing census of very early galaxies, based on UV measurements, remains incomplete. This revelation stems from a recent study published in Nature.

The breakthrough occurred in November 2019 when Fudamoto and colleagues employed the Atacama Large Millimeter/submillimeter Array (ALMA), an extraordinarily sensitive interferometer based in Chile. ALMA’s capabilities extend to surveying vast cosmic distances and peering through dusty cosmic environments to observe objects from an era known as “cosmic dawn” or the “epoch of reionization,” marking the birth of the first stars and galaxies.

REBELS-12 AND REBELS-29 DETECTED IN NEAR-INFRARED RADIATION WHILE REBELS-12-2 AND REBELS-29-2 HAVE NOT BEEN DETECTED IN THE NEAR-INFRARED, WHICH SUGGESTS THAT THESE GALAXIES ARE DEEPLY BURIED IN DUST. IMAGE: ALMA (ESO/NAOJ/NRAO), NASA/ESA HUBBLE SPACE TELESCOPE, ESO, FUDAMOTO ET AL.

Fudamoto’s team is part of the ALMA program called Reionization-Era Bright Emission Line Survey (REBELS), which has been dedicated to the study of 40 luminous galaxies from the cosmic dawn period. During their investigations of two specific galaxies, REBELS-12 and REBELS-29, the researchers noticed indistinct patterns of emissions located several thousand light years away from the known, brighter celestial sources.

Subsequent observations unveiled the true nature of these murky signals: two previously undiscovered galaxies that had been concealed behind thick veils of cosmic dust. Dubbed REBELS-12-2 and REBELS-29-2, these galaxies eluded detection in UV and optical spectra but became visible to ALMA owing to its ability to capture far-infrared wavelengths.

This serendipitous find suggests that as many as one in five galaxies from the cosmic dawn epoch may remain hidden behind cosmic dust clouds. This revelation carries profound implications for our understanding of the processes governing star and galaxy formation during this ancient cosmic era. Fudamoto and colleagues advocate for future surveys that reach deeper into the cosmos to detect fainter dust-obscured galaxies like REBELS-12-2 and REBELS-29-2, emphasizing the need for extensive, wide-area exploration.

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