Astronomers just got lucky.
A pair of ancient galaxies residing at the very edge of space and time were just discovered by a team of astronomers and scientists, hiding behind a thick veil of cosmic dust, according to a recent study published in the journal Nature.
The obscured galaxies came into being more than 13 billion years ago, roughly 800 million years after the Big Bang that gave life to the universe as we know it. And, there may be even more ancient objects lying in wait for us to pick out from the clutter of the universe’s messy beginnings.
Ancient galaxies from the dawn of the universe
It was sheer luck that the team of scientists saw the haunting spectral signals from the two galaxies. This incredible feat was accomplished by a team of frontier scientists led by Yoshinobu Fudamoto the National Astronomical Observatory of Japan (NAOJ), who is also an astronomer at the Research Institute for Science and Engineering at Waseda University, Japan. The team was looking at neighboring (younger) galaxies that shine far brighter in ultraviolet (UV) light, when they noticed something extra. And the “serendipitous discovery of these two dusty galaxies” at the very edge of the known universe “shows that our current (UV-based) census of very early galaxies is still incomplete,” according to the recent study.
And it was November 2019 when Fudamoto and his colleagues witnessed the galaxies lurking in an extremely distant era of the universe by employing the Atacama Large Millimeter / submillimeter Array (ALMA), which is a highly-sensitive interferometer in Chile. ALMA can observe objects at colossal distances, peering through dusty environments to glimpse objects that exist in the ancient epoch of the cosmos called the “cosmic dawn” or the “epoch of reionization,” when the very first galaxies and stars came into being.
This could transform the way we model the early universe
Part of a larger ALMA program called Reionization-Era Bright Emission Line Survey (REBELS), Fudamoto and his team have studied 40 luminous galaxies that existed in this nascent age of the universe. The team was observing two target galaxies, called REBELS-12 and REBELS-29, when they spotted blurry patterns of extra emissions emanating from a location several thousand light-years farther than the known brighter galaxies. Further observations confirmed that this team of astronomers and scientists was, in fact, staring at the faces of two previously unknown galaxies that had been hiding behind thick clouds of cosmic dust. They were subsequently named REBELS-12-2 and REBELS-29-2, and are invisible to both optical and UV light. ALMA could only detect them because of its heightened sensitivity to far-infrared wavelengths.
And so far, the discovery suggests that up to one in five galaxies residing in the time of the cosmic dawn could be lurking behind dark clouds of cosmic dust, which could transform the way we model star and galaxy formation during this ancient era of the universe. Fudamoto and his team think that “a blind, wide-area survey for such sources is required in the future,” according to the study. “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.” It’s incredibly satisfying to know that at the very dawn of the universe, entire galaxies teeming with stars were already thriving, only 800 million years after the Big Bang.