Scientists Accidentally Discovered Hidden Galaxies At the Edge of Time - Beyond The World
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Scientists Accidentally Discovered Hidden Galaxies At the Edge of Time

The unexpected result implies that one in every five galaxies in the ancient universe may be concealed behind dust.

Astronomers have discovered two galaxies at the end of space and time that had previously been covered under a thick veil of dust. The obscured galaxies formed more than 13 billion years ago, only about 800 million years after the universe’s beginning, and could aid scientists in the discovery of additional ancient objects obscured by dust.

Scientists led by Yoshinobu Fudamoto, an astronomer at Waseda University’s Research Institute for Science and Engineering and the National Astronomical Observatory of Japan (NAOJ), discovered the strange spectral signals from the two galaxies entirely by chance while studying neighboring galaxies that shine much brighter in ultraviolet (UV) light.

According to a paper published on Nature, the “serendipitous discovery of these two dusty galaxies” at the edge of the universe “shows that our current (UV-based) census of very early galaxies is still incomplete.”

Fudamoto and his colleagues detected galaxies in this ancient age of the universe in November 2019 using the Atacama Large Millimeter/submillimeter Array (ALMA), a highly sensitive interferometer in Chile. ALMA may view objects from an early age known as “cosmic dawn” or the “epoch of reionization,” when the first stars and galaxies formed, across great distances and through dusty environments.

Fudamoto and his colleagues are members of the ALMA initiative known as the Reionization-Era Bright Emission Line Survey (REBELS), which has been researching 40 brilliant galaxies that existed at the dawn of time. The researchers were looking at two target galaxies, REBELS-12 and REBELS-29, when they discovered blurry patterns of emissions located thousands of light years away from the known brighter sources.

Rebels-12 and Rebels-29 were detected in near-infrared radiation, but rebels-12-2 and rebels-29-2 were not, suggesting that these galaxies are deeply buried in dust. Image: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, ESO, Fudamoto et al.

Follow-up observations revealed that the unclear signals were actually two previously unknown galaxies hidden behind dense clouds of dust. The objects, known as REBELS-12-2 and REBELS-29-2 by Fudamoto’s team, are undetectable in UV and optical light and were only detected by ALMA because to its sensitivity to far-infrared wavelengths.

The lucky discovery implies that up to one in every five galaxies during cosmic dawn may be hidden under clouds of cosmic dust, which has ramifications for models of star and galaxy formation during this bygone era. In the study, Fudamoto and his colleagues recommend that “a blind, wide-area survey for such sources is required in the future.”

“These surveys must observe substantially deeper than had been envisioned previously to sample the fainter dust-obscured, but otherwise ‘normal’ galaxies such as REBELS-12-2 and REBELS-29-2,” the team concluded.

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