At the very center of our galaxy, behind dense clouds of interstellar dust, one of the most ancient objects we have managed to discern lay hidden for decades. The globular cluster VVV CL001, discovered back in 2010 as part of the VISTA Variables in the Vía Láctea survey, remained a mystery for a long time. It is too faint, too small and too heavily obscured to measure its distance and age accurately. Now a team of astronomers led by H. Olivares Carvajal of the Capodimonte Observatory (INAF) has managed to pierce this veil of dust.
The results of the study are set out in the paper “VVV CL001: A strong candidate for the most ancient star cluster in the Galaxy”, posted on 20 October 2026 on the arXiv preprint server and already accepted for publication in the authoritative journal Astronomy & Astrophysics. The work was carried out by a large international group of scientists, including specialists from Chile, Italy and other countries. It is this publication that for the first time provides such precise and consistent estimates of the cluster's key parameters.
The cluster lies in the direction of the galactic bulge — the densely populated central region of the Milky Way. The dust here is so thick that ordinary optical observations are almost useless. Previously, different groups obtained widely divergent estimates of the distance, and therefore of the orbit as well. Some even doubted whether it truly belongs to the bulge or is an interloper from the outer regions. The absence of RR Lyrae variable stars, which are usually used as “standard candles”, only made the task harder.
The researchers took deep infrared images with the FourStar camera on the 6,5-meter Magellan telescope and combined them with Hubble Space Telescope data, which suffer less from dust absorption. Using precise measurements of the stars' proper motions and machine-learning algorithms, they identified about 155 genuine cluster members. Among them, for the first time, they were able to reliably record stars on the horizontal branch and at the main-sequence turnoff — key evolutionary stages used to determine age and distance.
Comparison with theoretical models of stellar evolution gave a distance of 7,34 kiloparsecs (roughly 24 thousand light-years) with the smallest uncertainty to date. This confidently places VVV CL001 inside the bulge. And the age came out at 13,4 ± 0,4 billion years. For comparison: the age of the Universe itself is estimated at about 13,8 billion years. It follows that this cluster formed in the very first hundreds of millions of years after the Big Bang.
Its chemical composition only reinforces the impression. The metallicity [Fe/H] ≈ –2,2 is one of the lowest among known globular clusters of the bulge. Such metal-poor objects are usually regarded as relics of the earliest stages of the galaxy's formation. Orbital calculations confirm it: the cluster belongs to the inner region of the Milky Way and most likely formed in place rather than being captured later.
The novelty of the work lies in several aspects at once. First, the most accurate estimate to date of the distance to this heavily obscured object has been obtained. Second, stars at key evolutionary stages have been reliably identified for the first time, which made it possible to reconcile two independent methods of age determination and obtain a result with a small uncertainty. Third, the data indicate that VVV CL001 may be not merely one of the oldest, but the most ancient globular cluster in our entire galaxy, especially among bulge objects. This substantially broadens our understanding of the earliest stages of the Milky Way's assembly and of how quickly dense stellar systems could form within it.
If the age really is close to 13,4 billion years, then the galaxy must have managed to form such objects almost immediately after the birth of the Universe. Astronomers are already planning high-resolution spectroscopic observations to refine the chemical composition and definitively confirm the results.
Behind this dry figure of 13,4 billion years lies something far greater. In the chaos of the early Universe, when the first stars were only just beginning to enrich space with heavy elements, a dense, stable cluster had already managed to be born, one that survived all the subsequent turbulent development of the galaxy. It rotates calmly at its very heart, hidden by dust, and preserves within itself the memory of times when the cosmos was entirely different. Every such object is a living archive that reminds us: we exist in a world of incredible complexity and depth, where even in the darkest corners of our own galaxy evidence of its grand beginning continues to be revealed.
