{"id":976814,"date":"2026-05-22T02:26:20","date_gmt":"2026-05-22T02:26:20","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/976814\/"},"modified":"2026-05-22T02:26:20","modified_gmt":"2026-05-22T02:26:20","slug":"ultra-faint-dwarf-galaxies-could-unlock-secrets-of-the-early-universe","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/976814\/","title":{"rendered":"Ultra-Faint Dwarf Galaxies Could Unlock Secrets of the Early Universe"},"content":{"rendered":"

\"Simulated<\/a>(A) Dark matter distribution in our neighborhood in the Universe, the so-called Local Group of galaxies. The two large dark matter halos correspond to those of the Milky Way and Andromeda galaxy; (B) zoom-in on the dark matter in and around a small halo ~700 million years after the Big Bang; (C-1 and C-2) stars and gaseous material in the simulated ultra faint dwarf galaxy, hosted in the centre of the small dark matter halo in panel B, in two different models for the conditions of the early Universe. We can see how the ultra-faint dwarf galaxy changes its properties depending on the model. The scale on each image is in units of light years. (Image credit: J Sureda\/A Fattahi\/S Brown\/S Avraham) Credit: J Sureda\/A Fattahi\/S Brown\/S AvrahamTiny galaxies orbiting the Milky Way may hold clues to one of cosmology\u2019s biggest mysteries.<\/p>\n

Ultra-faint dwarf galaxies are among the smallest known galaxies orbiting the Milky Way. Astronomers have long viewed them as ancient remnants from the early cosmos. Now, researchers at the Oskar Klein Centre and the LYRA collaboration have used a powerful new set of simulations to show that these dim galaxies may reveal how conditions in the young Universe shaped which galaxies were able to grow and which never formed stars at all.<\/p>\n

The study, published in Monthly Notices of the Royal Astronomical Society (MNRAS), was led by Azadeh Fattahi, Associate Professor at the Oskar Klein Centre (OKC), along with collaborators from Durham University and the University of Hawaii.<\/p>\n

She explains the\u00a0scale of the project:\u00a0\u201cIn this work we presented a\u00a0brand-new\u00a0suite of cosmological simulations focused on the faintest galaxies in the Universe, with an unprecedented resolution. These are by\u00a0far the largest sample of such galaxies ever simulated at these resolutions.\u201d\u00a0<\/p>\n

Tiny Galaxies at the Edge of Understanding<\/p>\n

Dwarf galaxies are much smaller than the Milky Way and form inside small dark matter halos predicted by standard cosmological models. The faintest examples are extremely fragile and sit near the edge of what scientists currently understand about galaxy formation and dark matter.<\/p>\n

\u201cThe smallest galaxies are called ultra-faint dwarf galaxies, which are a million times less massive than the Milky Way or even\u00a0smaller,\u201d Fattahi says. \u201cDue to their small size these galaxies have proven very difficult to model and simulate.\u201d\u00a0<\/p>\n

\"Azadeh<\/a>Azadeh Fattahi, Associate Professor at the Oskar Klein Centre and the Department of Physics, Stockholm University. Credit: Samuel Avraham<\/p>\n

The new simulations provide researchers with a much clearer and more systematic picture of how these galaxies formed over cosmic history.<\/p>\n

\u201cA useful analogy is to plants and crops and how the way they grow is sensitive to the weather conditions\u201d, says Shaun Brown who led the study while working at OKC and Durham University. \u201cIn the same way that the yield of a crop in summer can indirectly tell you a lot about what the weather in spring must have been like, the properties of faint dwarf galaxies today can tell us a lot about the conditions, or weather, of the Universe at a much earlier time.\u201d\u00a0<\/p>\n

A Window Into the Early Universe<\/p>\n

The simulations are especially important because they do more than recreate faint dwarf galaxies. They also suggest that these nearby objects can reveal information about the Universe\u2019s earliest \u201cclimate.\u201d The team tested how different ideas about early radiation conditions affected whether small dark matter halos could form stars.<\/p>\n

\u201cIn the paper we studied two different assumptions about the properties of the early Universe when it was less than 500 million years old, to understand the effect on the properties of these small galaxies today when the Universe is 13 billion years old,\u201d Brown explains.<\/p>\n

The results showed a strong effect in the smallest galaxies.<\/p>\n

\u201cWe found that these small ultra-faint galaxies are very sensitive to these changes, while more massive galaxies, like our Milky Way, don\u2019t really care,\u201d he adds. \u201cFor the smallest galaxies, early conditions can decide whether they become visible galaxies, or remain starless dark matter halos.\u201d<\/p>\n

This sensitivity could help scientists test ideas about early-Universe physics with future observations.<\/p>\n

\u201cExcitingly, in the near future we will have data from the Vera C. Rubin Observatory which will be able to find many more of these ultra-faint dwarfs around the Milky Way,\u201d says Fattahi.<\/p>\n

Future Observations Could Test the Theory<\/p>\n

Astronomers hope the Vera C. Rubin Observatory will uncover nearly all of the Milky Way\u2019s satellite galaxies. According to the new study, those discoveries may also provide insights into conditions that existed shortly after the Big Bang.<\/p>\n

\u201cOur work suggests that these upcoming observations of the very local Universe will be able to constrain what the Universe at its infancy looked like, something we currently cannot directly access with other observations.\u201d<\/p>\n

The findings also connect to recent discoveries from the James Webb Space Telescope (JWST), which has detected unexpectedly massive and bright galaxies in the early Universe.<\/p>\n

\u201cThe result is particularly relevant in light of recent discoveries of galaxies in the early Universe, by the James Webb Space Telescope (JWST), which is finding many surprises, in particular unexpectedly massive and bright galaxies in the early universe,\u201d Fattahi notes.<\/p>\n

If distant galaxies are challenging current theories about the early cosmos, nearby ultra-faint dwarf galaxies may offer another way to investigate what happened during that period.<\/p>\n

Massive Simulations and Future Questions<\/p>\n

Studying galaxies this faint required major computing power.<\/p>\n

\u201cRunning these simulations is challenging, and extremely expensive in both time and computational resources,\u201d Fattahi says.<\/p>\n

Altogether, the simulations took more than six months to run. They also produced an enormous amount of data.<\/p>\n

\u201cThe simulation also produces very large amounts of data (in total approximately 300 TB). This meant many of the old algorithms designed for smaller amounts of data needed updating and improving to effectively handle this new large amount of data.\u201d<\/p>\n

Most of the work was performed on COSMA 8, a supercomputer built for simulation-based research. COSMA 8 is hosted by Durham University\u2019s Institute for Computational Cosmology on behalf of the UK\u2019s DiRAC High Performance Computing Facility.<\/p>\n

Fattahi\u2019s team now plans to use the simulation suite to explore major unanswered questions in galaxy and structure formation. These include where the first generation of stars in the Universe might be found and what ultra-faint dwarf galaxies can reveal about the nature of dark matter.<\/p>\n

Reference: \u201cLYRA ultra-faints: the emergence of faint dwarf galaxies in the presence of an early Lyman\u2013Werner background\u201d by Shaun T Brown, Azadeh Fattahi, Thales A Gutcke, Sylvia Ploeckinger, Joaquin Sureda, Sownak Bose, Jessica E Doppel, R\u00fcdiger Pakmor and Adrian Jenkins, 24 April 2026,\u00a0Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093\/mnras\/stag439<\/a><\/p>\n

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