In the early universe, monstrous black holes may have formed with the assistance of ultralight dark matter.

Scientists have long been baffled by the origins of the most monstrous black holes in the universe. In the heart of galaxies less than a billion years after the Big Bang, supermassive black holes (SMBHs) that are billions of times larger than the Sun have been discovered. The inquiry is: how did these cosmic giants expand in such a short amount of time? One possible solution is being revealed by a brand-new theoretical model, and it involves ultralight dark matter (ULDM), one of the universe's most elusive elements. The Problem of Black Hole Growth Smaller "seed" black holes, which form when massive stars collapse, are thought to grow into supermassive black holes. However, even under the most favorable circumstances, it seems implausible that standard accretion—the gradual feeding of gas and matter—can form black holes of billions of solar masses in less than a billion years. Because of this inconsistency, physicists and cosmologists have looked into bizarre possibilities, such as the influence of alternative forms of dark matter, a mysterious substance that only weakly interacts with light and normal matter but makes up about 85% of all matter in the universe. What exactly is ultralow dark matter? Particles of ultralight dark matter have masses on the order of 10⁻²²electronvolts, or roughly 10⁻⁵⁰times that of an electron. In some models, this wave-like structure of matter is referred to as a Bose-Einstein condensate because these particles exhibit quantum behavior on galactic scales due to their small mass. In contrast to the clumpy, halo-like distributions associated with conventional cold dark matter (CDM), these quantum fluctuations produce interference patterns and structures. One intriguing result is that ULDM could naturally result in dense regions that could much more effectively seed black hole formation than CDM. Accelerating the Growth of Black Holes These dense regions created by ULDM, according to recent simulations and theoretical work, can accelerate the formation and growth of black holes in two main ways: Solitonic cores, stable, dense regions in the center of dark matter halos, can be formed as a result of the wavelike nature of ULDM. These regions can quickly collapse or funnel gas toward a central seed, giving black holes a head start in their growth.

ULDM can smooth out velocity dispersions and prevent small-scale structure formation, both of which reduce angular momentum in gas clouds that are collapsing. Matter can now fall directly into black holes rather than continue to orbit indefinitely because of this. Implications for Observations of the Early Universe At earlier cosmic epochs than anticipated, the James Webb Space Telescope (JWST) and other next-generation observatories have already begun to find SMBHs. ULDM-based models can benefit greatly from these observations. If ULDM played a significant role in the formation of SMBHs, its effects could have an impact not only on the distribution of galaxies and the cosmic microwave background but also on black holes. Researchers hope to differentiate ULDM's subtle signatures from those of CDM or other exotic physics as data accumulate. Obstacles and the Way Forward Although ULDM provides an elegant solution to the problem of rapidly expanding black holes, it is still only a theoretical possibility. Constraints imposed by galactic rotation curves, gravitational lensing studies, and Lyman-alpha forest observations, all of which test dark matter behavior at various scales, present obstacles. However, the increasing amount of evidence from early universe SMBHs is prompting scientists to consider alternatives to conventional models. Regardless of whether or not ULDM is the true nature of dark matter, it is a compelling possibility that continues to motivate innovative research into the cosmos' hidden scaffolding.