Astronomers using the Hubble Space Telescope have discovered an entirely new type of cosmic object that contains no stars. This structure, composed of dark matter and gas, was detected in the outer regions of the spiral galaxy Messier 94 (M94), approximately 14 million light-years from Earth. Scientists, reflecting the excitement of the discovery, named this object “Cloud 9”.
Cloud 9 stands out not only for its unusual structure but also for holding critical clues about how galaxies formed in the early universe. According to researchers, this object offers a rare observational opportunity to understand how dark matter coalesces to form the foundations of galaxies.
A Failed Galaxy Without Stars
Andrew Fox of AURA/STScI, working on behalf of the European Space Agency (ESA), summarizes the importance of Cloud 9 by saying, “This cloud is a window into the dark universe.” According to the scientific community, approximately 85% of the total matter in the universe consists of dark matter. However, because dark matter does not interact with light, it cannot be observed directly, and its existence can only be inferred through gravitational effects.
Cloud 9 presents a unique example in this regard. Despite being a cloud dominated by dark matter, it contains no stars. This situation supports a cosmic scenario that has long been theoretically predicted but never directly confirmed until now.
Scientifically classified as a RELHIC (Reionization-Limited Hydrogen I Cloud), Cloud 9 contains hydrogen gas. Under normal circumstances, star formation is expected to begin in such dense gas clouds. However, this process has not occurred in Cloud 9. Researchers believe the primary reason for this is that not enough gas accumulated to trigger star formation.
Alejandro Benitez-Llambay, the study's lead, describes this situation by saying, “This is the story of a failed galaxy.” According to Benitez-Llambay, the absence of stars is the strongest element proving the theory's validity. This is because Cloud 9 represents a primordial galactic building block that has remained undisturbed in the local universe to this day.
Scientists had long theoretically predicted the existence of RELHICs. However, without Hubble's high sensitivity, the discovery of Cloud 9 might not have been possible. This discovery suggests that other “frozen” or underdeveloped galaxies similar to Cloud 9 may exist in the universe.
A Small but Extremely Dense Structure
Cloud 9 possesses characteristics that should not be confused with the hydrogen clouds known around the Milky Way. The structure is smaller, more compact, and exhibits an almost perfectly spherical form. The cloud, whose core consists of neutral hydrogen, has a diameter of approximately 4,900 light-years. While the total mass of hydrogen gas is estimated to be about 1 million times that of the Sun, the dark matter mass is thought to reach 5 billion solar masses.
According to the research team, if Cloud 9 can accumulate enough hydrogen gas in the future—approximately 5 billion solar masses—it has the potential to transform into a star-filled galaxy. Astronomers hope to find more RELHICs similar to Cloud 9 in the future.
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