"Hidden galaxies" discovery would upend our current understanding of the universe

A newly analyzed, deep-field universe photo, produced by stacking multiple infrared observations, points to elusive collections of dust-filled star systems. This intriguing view of ancient “hidden galaxies” could change how we understand the cosmos.

Researchers used cutting-edge imaging to map a far-infrared landscape brimming with nearly 2,000 galaxies.

Preliminary hints suggest there may be galaxies lurking just out of sight, influencing how energy is emitted across space.

Early calculations indicate that their collective light might explain the missing piece in the energy puzzle at long infrared wavelengths, an aspect that has puzzled astronomers for years.

Searching the infrared for hidden galaxies

Observing the universe in infrared light has expanded our ability to see objects that remain hidden to optical telescopes.

This part of the spectrum reveals cooler regions where dust particles radiate energy at wavelengths beyond the range of human eyes.

Researchers have used this approach to chart stellar nurseries, probe galactic cores, and examine phenomena where dust clouds block traditional views.

Early forays into infrared studies began in the 19th century, soon after the discovery of this invisible band of light. Over time, balloon-borne and space-based observatories advanced what ground-based telescopes could accomplish.

They offered stable platforms free from most atmospheric interference, allowing investigators to map star formation on scales that once seemed unreachable.

Herschel-SPIRE Dark Field

Dr. Chris Pearson from STFC RAL Space and Imperial College London has been leading efforts to analyze these findings. He contributed to a set of papers detailing how this survey has charted previously unseen regions.

“This work has pushed the science with Herschel to its absolute limit, probing far below what we can normally discernibly see and potentially revealing a completely new population of galaxies that are contributing to the very faintest light we can observe in the universe,” Pearson explained.

The newly processed image, known as the Herschel-SPIRE Dark Field, is touted as the deepest far-infrared view ever achieved.

It was created by stacking 141 separate images gathered by the Herschel Space Observatory’s SPIRE instrument, which ran from 2009 to 2013.

Combining these layers has allowed astronomers to track dust-obscured star formation and measure how each galaxy’s brightness affects the total energy flow coursing through space.

Disrupting established models

Preliminary results have raised eyebrows among experts. The possible galaxies may also provide the missing piece of the puzzle for energy generation in the universe’s infrared light.

Observers suggest that their combined glow might fill a gap in the measured background radiation, bringing it in line with what theory predicts.

Hidden galaxies and statistics

Thomas Varnish, a PhD student at the Massachusetts Institute of Technology (MIT), contributed a second paper on these findings.

“We employed statistical techniques to get around this overcrowding, analyzing the blurriest parts of the image to probe and model the underlying distribution of galaxies not individually discernible in the original image,” Varnish noted.

“What we found was possible evidence of a completely new, undiscovered population of faint galaxies hidden in the blur of the image, too faint to be detected by conventional methods in the original analysis.”

As far as Varnish is concerned, if this discovery is confirmed, this new population would effectively break all of our current models of galaxy numbers and evolution.

Peering into the dusty universe

Scientists emphasize that half of cosmic activity can be missed if observations are limited to visible light.

When we look at starlight through normal telescopes, we are only able to read half of the story of our universe. The other half is hidden, obscured by the intervening dust.

In fact, roughly half of the energy output of the universe is from starlight that has been absorbed by dust and re-emitted as cooler infrared radiation.

To fully understand the evolution of our universe we need to observe the sky in both optical and longer wavelength infrared light.”

This perspective guided the Herschel mission, which leveraged the SPIRE instrument to scan a single dark patch in the sky as a regular calibration target during its four-year run.

What happens next?

Imperial College London astrophysicist Dr. David Clements, who was also involved in the research.

“These results show just how valuable the Herschel archive is. We’re still getting great new results more than 10 years after the satellite stopped operating,” Dr. Clements added.

The James Webb Space Telescope has since taken over as the largest infrared telescope, but it cannot duplicate the same far-infrared sensitivity previously provided by Herschel.

“What we can’t get, though, is more data at these wavelengths to follow up these fascinating new results. For that we need the next generation far-IR mission, PRIMA, currently being proposed to NASA,” Clements concluded.

The concept involves a 1.8-meter telescope designed for imaging and spectroscopy at far-infrared wavelengths, bridging gaps left by existing observatories.

What these hidden galaxies teach us

To sum it all up, we now know there’s a whole hidden side of the universe revealed by far-infrared observations, and the Herschel-SPIRE Dark Field study makes that clearer than ever.

Researchers stacked numerous images to uncover previously invisible galaxies that might close the gap in our understanding of cosmic energy output.

This discovery suggests that half the story – shrouded by dust and missed by optical telescopes – actually plays a huge role in shaping how galaxies form and evolve.

And with future missions like PRIMA in the works, we’ll likely find even more surprises waiting in these obscured regions of space.

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Click here to watch a video on the SPIRE Dark Field animation…

The full study was published in the journal Monthly Notices of the Royal Astronomical Society.

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