Free Astronomy Magazine March-April 2026

MARCH-APRIL 2026 A team using the NASA/ESA Hub- ble Space Telescope has uncov- ered a new type of astronomical object —a starless, gas-rich, dark- matter cloud that is considered a “relic” or remnant of early galaxy formation. Nicknamed “Cloud-9,” this is the first confirmed detection of such an object in the Universe. This image shows the blank field of the surrounding region of Cloud-9. [NASA, ESA. G. Anand (STScI), and A. Benitez-Llambay (Univ. of Milan- Bicocca); Image processing: J. De- Pasquale (STScI)] Scientists have been studying hydro- gen clouds near the Milky Way for many years, and these clouds tend to be much bigger and irregular than Cloud-9. Compared with other observed clouds, Cloud-9 is smaller, more compact, and highly spherical, making it look very different from other clouds. The core of this object is composed of neutral hydrogen and is about 4,900 light-years in di- ameter. The hydrogen gas in Cloud- 9 is approximately 1 million times the mass of the Sun. But if the pres- sure of the gas is balancing the grav- ity of the dark matter cloud, which it appears to be, Cloud-9 must be heavily dominated by dark matter, at about 5 billion solar masses. Cloud-9 is an example of the struc- tures and the mysteries that don’t involve stars. Just looking at stars doesn’t give the full picture. Studying the gas and dark matter helps provide a more complete un- derstanding of what’s going on in these systems that otherwise would- n’t be known. Observationally, iden- tifying these failed galaxies is chal- lenging because nearby objects out- shine them. Such systems are also vulnerable to environmental effects like ram-pressure stripping, which can remove gas as the cloud moves through intergalactic space. These factors further reduce their expected numbers. The starless relic was dis- covered three years ago as part of a radio survey by the Five-hundred- meter Aperture Spherical Telescope (FAST) in Guizhou, China, a finding later confirmed by the Green Bank Telescope and the Very Large Array facilities in the United States. But only with Hubble could re- searchers definitively determine that the failed galaxy contains no stars. Cloud-9 was simply named sequen- tially, having been the ninth gas cloud identified on the outskirts of a nearby spiral galaxy, Messier 94 (M94). The cloud is close to M94 and appears to have a physical associa- tion with the galaxy. High-resolution radio data shows slight gas distor- tions, possibly indicating interaction between the cloud and galaxy. The cloud may eventually form a galaxy in the future, provided it grows more massive — although how that would occur is under speculation. If it were much bigger, say, more than 5 billion times the mass of our Sun, it would have collapsed, formed stars, and become a galaxy that would be no different than any other galaxy we see. If it were much smaller than that, the gas could have been dispersed and ionized and there wouldn’t be much left. But it’s in a sweet spot where it could re- main as a RELHIC. The lack of stars in this object provides a unique win- dow into the intrinsic properties of dark matter clouds. The rarity of such objects and the potential for fu- ture surveys is expected to enhance the discovery of more of these “failed galaxies” or “relics,” result- ing in insights into the early universe and the physics of dark matter. !