Astronomers utilizing the NASA/ESA Hubble Space Telescope have verified the presence of a starless, hydrogen-rich object primarily composed of dark matter. These intriguing entities, referred to as reionization-limited HI clouds (RELHICs), are remnants of the early Universe. They pose challenges to traditional theories of galaxy formation and may indicate undiscovered populations of similar cosmic structures.
This image illustrates the location of RELHIC object Cloud-9. Image credits: NASA / ESA / VLA / Gagandeep Anand, STScI / Alejandro Benitez-Llambay, University of Milan-Bicocca / Joseph DePasquale, STScI.
The RELHIC object, known as Cloud-9, was detected using the 500-meter Aperture Spherical Telescope (FAST) and its existence was independently verified by the Very Large Array (VLA) and the Green Bank Telescope (GBT).
“This is the narrative of a failed galaxy,” states astronomer Alejandro Benítez Lambay from the University of Milano-Bicocca.
“Scientific advancements often arise from failures rather than successes. In this case, the absence of stars confirms our theoretical framework,” he adds.
“This discovery reveals primordial components of galaxies yet to form within our local universe.”
The core of Cloud-9 consists of neutral hydrogen and spans approximately 4,900 light-years in diameter.
This object is positioned in proximity to the spiral galaxy Messier 94, shares its recession velocity, and is approximately 14.3 million light-years away from Earth.
“Cloud-9 represents a crucial glimpse into the enigmatic dark universe,” remarked Dr. Andrew Fox, an astronomer at ESA’s Association of Universities for Astronomical Research/Space Telescope Science Institute (AURA/STScI).
“Theoretical models suggest that a majority of the universe’s mass is composed of dark matter, which does not emit light, thus making it challenging to detect.”
“Cloud-9 offers a rare opportunity to study clouds dominated by dark matter.”
Astronomers employed Hubble’s Advanced Camera for Surveys (ACS) to search for bright stellar components within Cloud-9.
The findings discount the presence of dwarf galaxies with detectable stellar masses.
“The lack of observable stars reinforces the interpretation of this system as a RELHIC—a starless dark matter halo filled with hydrostatic gas in thermal equilibrium with the cosmic ultraviolet background,” stated the researchers.
Cloud-9 stands as a prime candidate for a compact HI cloud and offers robust empirical support for the ΛCDM (lambda cold dark matter) model, a leading cosmological framework.
This model predicts the existence of a starless dark matter halo filled with gas on subgalactic mass scales that have yet to form stars.
“The discovery of Cloud-9 also refines the current thresholds for halo mass required for galaxy formation, bringing us closer to understanding why some dark matter halos host galaxies while others remain barren,” concluded the researchers.
For detailed findings, look for the upcoming publication in the Astrophysics Journal Letter.
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Gagandeep S. Anand et al. 2025. The first RELHIC? Cloud-9 is a starless gas cloud. APJL 993, L55; doi: 10.3847/2041-8213/ae1584
Source: www.sci.news
