A domestic research team has discovered the traces of a massive collision that occurred in the Perseus galaxy cluster about 5 billion years ago, marking the world's first identification of such evidence using cutting-edge observational techniques.
The research team from Yonsei University, a prominent institution in the field, noted on the 21st that the Perseus galaxy cluster, which has long been regarded in the astronomical community as a representative case of a stable cluster, actually harbors evidence of a violent collision in its past. The research findings were published in the international scientific journal "Nature Astronomy" on the 16th.
A galaxy cluster is a massive structure formed by the aggregation of thousands of galaxies, about 80% of its mass composed of invisible dark matter. Galaxy clusters are considered key to studying the evolution of the universe because they grow through repeated collisions and mergers. However, the Perseus galaxy cluster, which is 600 trillion times the mass of Taeyang, has been known as an exception due to the absence of discovered collision traces.
The research team searched for signs of minute collisions remaining in the Perseus galaxy cluster based on data from the Subaru Telescope of the National Astronomical Observatory of Japan. As a result, it was confirmed that a dark matter lump, 200 trillion times the mass of Taeyang, exists about 1.4 million light-years (1 light-year is the distance light travels in one year, approximately 9.46 trillion kilometers) away from the center of the Perseus galaxy cluster, and that this mass is connected to the main body of the cluster by a "dark matter bridge." This is interpreted as direct evidence that the two celestial bodies actually collided in the past.
Through computer simulations, the research team confirmed that this dark matter structure caused a collision with the Perseus galaxy cluster about 5 billion years ago, and that traces of this collision remain in the current structure of the cluster.
The professor from Yonsei University remarked, "Although the Perseus galaxy cluster has been perceived as stable until now, this research will fundamentally change that perception," adding, "We plan to conduct follow-up simulation studies on how particle acceleration occurs during the cluster collision process."
References
Nature Astronomy (2025), DOI: https://www.nature.com/articles/s41550-025-02530-w