Astronomers spot one of the largest rotating structures in the universe

This enormous chain of hundreds of galaxies – a cosmic filament – ​​winds through space 400 million light years away.

By Humberto Basilio edited by Sarah Lewin Frasier

The first time Oxford University astronomer Lyla Jung saw the cosmic pattern on her monitor, she almost didn’t believe it was real. But it was – and Jung and his colleagues went on to identify one of the largest rotating structures ever discovered in space: a string of galaxies embedded in rotating space. cosmic filament 400 million light years from Earth.

The discovery, published in Monthly Notices of the Royal Astronomical Societycould give astronomers new insights into the formation, evolution and diversity of galaxies, Jung says.

Galaxies are not randomly or uniformly positioned in the universe; instead, they are connected in structures called filaments that connect them, along with dark matter, across space. With voids (empty spaces that contain very little matter) and groups of hundreds of thousands of galaxies called clusters, filaments form. what astronomers call the cosmic web.

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These filaments are the main channels through which matter flows, powering galaxies and clusters as structures develop. “By studying filaments, we understand how large-scale structures form and how galaxies acquire their spins,” says Peng Wang, an astrophysicist at the Shanghai Astronomical Observatory, who was not involved in the new study.

In 2021, Wang and colleagues reported that, based on calculations and satellite images, several filaments appeared to be rotating. The new study takes a closer look at one of these structures. Using data from the MeerKAT radio telescope in South Africa, which was helping map cold hydrogen in nearby galaxies, Jung’s team discovered 14 hydrogen-rich galaxies arranged in a thin structure 5.5 million light years away. This structure was embedded in a filament 50 million light years long and containing more than 280 galaxies.

The researchers observed that many of the individual galaxies detected by MeerKAT were rotating, and to their surprise, they also found that the entire filament, including the rest of its galaxies, appeared to be rotating in sync with this rotation at a speed of about 110 kilometers per second, something astronomers had never seen before. “I started to doubt whether it was real or whether I had done something wrong in the analysis,” says Jung.

Detection of this phenomenon “is exceptional,” Wang adds, because the observation signal is weak and overlapping objects along the line of sight can blur the image without very careful data collection and modeling.

In subsequent analyses, Jung and his team found that the filament was likely absorbing even more material. Many of its galaxies appear to be in the early stages of growth, she says, because they appear rich in the hydrogen that provides fuel for new stars.

One of the most compelling evidence for the existence of dark matter comes from measurements of the rotation of galaxies. Studying the filaments’ rotation could also reveal how much dark matter they contain, says astronomer Noam Libeskind of the Leibniz Institute for Astrophysics in Potsdam, Germany, who was not involved in the study. By revealing how much of the universe exists in these filaments, Libeskind says, this and future studies like it offer “a way to measure the dark matter content of the universe.”