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Galaxies on a Grand Scale: Astronomers Discover a Rotating Cosmic Filament
An international team has identified one of the largest rotating structures ever observed, offering new clues about how galaxies form.
- Cosmic filaments, the largest known structures in the universe, act as pathways for matter and angular momentum.
- Researchers discovered a 5.5 million light-year-long chain of galaxies rotating with the larger filament it resides within.
- The filament’s rotation speed is estimated at 110 km/s, and its discovery challenges existing models of galaxy formation.
- This “fossil record of cosmic flows” could refine measurements in upcoming weak lensing surveys.
Imagine a cosmic teacup ride, but instead of people, you have galaxies, and instead of a platform, you have a structure stretching millions of light-years. That’s the picture painted by a new discovery: an international research team led by the University of Oxford has identified one of the largest rotating structures ever observed – a razor-thin chain of galaxies embedded within a vast cosmic filament located about 140 million light years from Earth. The findings, published in Monthly Notices of the Royal Astronomical Society, may provide important clues about how galaxies formed in the early Universe. Understanding how galaxies acquire their spin is a fundamental question in cosmology, and this filament offers a unique opportunity to investigate this process.
Cosmic Web and Filamentary Structures
Cosmic filaments are the biggest known structures in the Universe, enormous thread-like networks of galaxies and dark matter that create the framework of the cosmic web. These filaments funnel matter and angular momentum into galaxies. Filaments where many galaxies spin in the same direction, and where the entire structure itself appears to rotate, are especially valuable for studying how galaxies acquired their spin and gas, and for testing ideas about how rotation develops across tens of millions of light years.
A Razor-Thin Line of Galaxies
In this study, researchers identified 14 nearby galaxies rich in hydrogen gas arranged in a narrow, elongated line measuring about 5.5 million light years in length and roughly 117,000 light years across. This thin structure lies within a much larger cosmic filament that stretches about 50 million light years and contains more than 280 additional galaxies. Remarkably, many of the galaxies in this strand appear to be rotating in the same direction as the filament itself, far more often than would be expected by chance. This finding suggests that large-scale cosmic structures may shape galaxy rotation more strongly or over longer periods than previously believed.
The team also found that galaxies on opposite sides of the filament’s central spine are moving in opposite directions, indicating the entire filament is rotating as a single structure. By applying models of filament dynamics, they estimated a rotation speed of about 110 km/s and calculated that the dense central region of the filament has a radius of approximately 50 kiloparsecs (about 163,000 light years).
“Teacups” in a Cosmic Ride
Co-lead author Dr. Lyla Jung (Department of Physics, University of Oxford) explained the significance of the discovery: “What makes this structure exceptional is not just its size, but the combination of spin alignment and rotational motion. You can liken it to the teacups ride at a theme park. Each galaxy is like a spinning teacup, but the whole platform – the cosmic filament – is rotating too. This dual motion gives us rare insight into how galaxies gain their spin from the larger structures they live in.”
The filament appears to be relatively young and undisturbed, described as a “dynamically cold” state. Its abundance of gas-rich galaxies suggests it is still in an early stage of development. Because hydrogen is crucial for forming new stars, these galaxies are actively collecting the fuel needed for star formation. Studying these systems offers a valuable view into early or ongoing phases of galaxy evolution.
Tracing Cosmic Gas Flows
Hydrogen-rich galaxies also serve as effective tracers of how gas moves along cosmic filaments. Atomic hydrogen is easily influenced by motion, revealing how gas flows through filaments and into galaxies. These observations help scientists understand how angular momentum moves through the cosmic web and shapes galaxy structure, rotation, and star formation.
The discovery may also help refine models of intrinsic galaxy alignments, which can interfere with measurements in upcoming weak lensing surveys, including missions such as the European Space Agency’s Euclid spacecraft and observations from the Vera C. Rubin Observatory in Chile.
Co-lead author Dr. Madalina Tudorache (Institute of Astronomy, University of Cambridge / Department of Physics, University of Oxford) said: “This filament is a fossil record of cosmic flows. It helps us piece together how galaxies acquire their spin and grow over time.”
Combining Observational Power
The research team used data from South Africa’s MeerKAT radio telescope, comprised of 64 interconnected dishes. The spinning filament was identified through a deep sky survey known as MIGHTEE, led by Professor of Astrophysics Matt Jarvis (Department of Physics, University of Oxford). The radio data were combined with optical observations from the Dark Energy Spectroscopic Instrument (DESI) and the Sloan Digital Sky Survey (SDSS), revealing the cosmic filament’s coordinated galaxy spin and large-scale rotation.
Professor Jarvis said: “This really demonstrates the power of combining data from different observatories to obtain greater insights into how large structures and galaxies form in the Universe. Such studies can only be achieved by large groups with diverse skillsets, and in this case, it was really made possible by winning an ERC Advanced Grant/UKIR Frontiers Research Grant, which funded the co-lead authors.”
The study also included researchers from University of Cambridge, University of the Western Cape, Rhodes University, South African Radio Astronomy Observatory, University of Hertfordshire, University of Bristol, University of Edinburgh, and University of Cape Town.
