Astronomers have identified the smallest dark object ever detected in the universe, a discovery that could reshape our understanding of dark matter.

The object, which does not emit light or radiation, was found using a global network of radio telescopes and is estimated to have a mass around one million times that of the Sun.

The breakthrough, detailed in two papers published on 9 October in Nature Astronomy and Monthly Notices of the Royal Astronomical Society, hinges on the phenomenon of gravitational lensing. This effect occurs when a massive object bends the light from a more distant source, allowing scientists to infer the presence and mass of otherwise invisible matter.

In this case, the object was so small that it revealed itself only through a minute distortion in the lensing pattern of a much larger object, akin to a subtle flaw in a funhouse mirror. “It’s an impressive achievement to detect such a low mass object at such a large distance from us,” said Professor Chris Fassnacht of the University of California, Davis, a co-author of the study. “Finding low-mass objects such as this one is critical for learning about the nature of dark matter.”

The true identity of the object remains uncertain. It could be a dense clump of dark matter, significantly smaller than any previously observed, or perhaps a compact, dormant dwarf galaxy. Either possibility would have profound implications for cosmology.

Dark matter, which makes up roughly a quarter of the universe, cannot be seen directly but is believed to play a crucial role in shaping the structure of galaxies and the cosmos at large. One of the central questions in astrophysics is whether dark matter can exist in small, starless clumps. Confirming this would support certain models of dark matter, particularly the cold dark matter theory.

To make the discovery, the research team employed an array of powerful instruments, including the Green Bank Telescope in West Virginia, the Very Long Baseline Array in Hawai‘i, and the European Very Long Baseline Interferometric Network. Together, these facilities formed a virtual Earth-sized telescope capable of detecting the faintest gravitational lensing signals.

The newly discovered object is at least one hundred times less massive than any previously found using this method. “Given the sensitivity of our data, we were expecting to find at least one dark object, so our discovery is consistent with the so-called cold dark matter theory on which much of our understanding of how galaxies form is based,” said lead author Devon Powell of the Max Planck Institute for Astrophysics in Germany. “Having found one, the question now is whether we can find more and whether the numbers will still agree with the models.”

The team is continuing to analyse the data in hopes of uncovering further examples of such elusive objects elsewhere in the sky. Their findings could help refine or challenge prevailing theories about the composition and behaviour of dark matter.

The international collaboration includes researchers from the University of Groningen, the South African Radio Observatory, the University of Pretoria, the Istituto di Radioastronomia in Bologna, and the Max Planck Institute for Astrophysics. The project received support from the European Research Council, the Italian Ministry of Foreign Affairs and International Cooperation, and the National Research Foundation of South Africa. The National Radio Astronomy Observatory, a facility of the US National Science Foundation, also contributed to the effort.