Free Astronomy Magazine March-April 2026

13 MARCH-APRIL 2026 ASTRO PUBLISHING ground-based telescopes. They just didn’t go deep enough in sensitivity to uncover stars,” explained lead au- thor Gagandeep Anand of STScI. “But with Hubble’s Advanced Cam- era for Surveys, we’re able to nail down that there’s nothing there.” The discovery of this relic cloud was a surprise. “Among our galactic neigh- bors, there might be a few aban- doned houses out there,” said STScI’s Rachael Beaton, who is also on the research team. RELHICs are thought to be dark matter clouds that were not able to accumulate enough gas to form stars. They represent a win- dow into the early stages of galaxy formation. Cloud-9 suggests the existence of many other small, dark matter-dom- inated structures in the Universe — other failed galaxies. This discovery provides new insights into the dark components of the Universe that are difficult to study through traditional observations, which focus on bright objects like stars and galaxies. T his image shows the location of Cloud-9. The diffuse magenta is radio data from the ground-based Very Large Array (VLA) showing the presence of the cloud. The dashed cir- cle marks the peak of radio emission, which is where researchers focused their search for stars. Follow-up ob- servations by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys found no stars within the cloud. The few objects that appear within its boundaries are background galaxies. Before the Hubble observa- tions, scientists could argue that Cloud-9 is a faint dwarf galaxy whose stars could not be seen with ground-based telescopes due to the lack of sensitivity. Hubble’s Ad- vanced Camera for Surveys shows that, in reality, the failed galaxy contains no stars. [NASA, ESA. G. Anand (STScI), and A. Benitez-Llam- bay (Univ. of Milan-Bicocca); Image processing: J. DePasquale (STScI)] “We know from theory that most of the mass in the Universe is expected to be dark matter, but it’s difficult to detect this dark material because it doesn’t emit light. Cloud-9 gives us a rare look at a dark-matter-dom- inated cloud.” The object is called a Reionization-Limited H I Cloud, or “RELHIC.” The term “H I” refers to neutral hydrogen, and “RELHIC” de- scribes a natal hydrogen cloud from the Universe’s early days, a fossil leftover that has not formed stars. For years, scientists have looked for evidence of such a theoretical phan- tom object. It wasn’t until they turned Hubble toward the cloud, confirming that it is indeed starless, that they found support for the the- ory. “Before we used Hubble, you could argue that this is a faint dwarf galaxy that we could not see with