Most distant Milky-Way-like galaxy discovered

A recent observation by the Very Large Telescope (VLT), operated by the European Southern Observatory (ESO), has provided remarkable insights into the merger of two galaxy clusters, Abell 115. Located over two billion light-years away, the system's complex structure and dynamics offer a glimpse into how cosmic phenomena unfold on grand scales.

Most distant Milky-Way-like galaxy discovered

Abell 115 consists of two subclusters, each hosting hundreds of galaxies, locked in a cosmic collision. The VLT's high-resolution imaging, combined with data from the Atacama Large Millimeter/submillimeter Array (ALMA), revealed gas structures and magnetic fields entwined in this cataclysmic event. As these two massive clusters merge, their interaction releases vast amounts of energy, generating shock waves that heat the surrounding gas to millions of degrees. This leads to the emission of X-rays, providing crucial insights into the nature of galaxy cluster mergers.

Moreover, the merger process has implications for understanding dark matter distribution. Through gravitational lensing, astronomers were able to map the elusive dark matter within the system. Abell 115’s gravitational potential, influenced by dark matter, distorts the light from background objects, enabling researchers to better understand the distribution of this invisible mass. The presence of radio halos in the system, formed by energetic particles accelerated during the collision, was another key finding. These halos serve as tracers for the magnetic fields and turbulent conditions within the system.

The southern Milky Way above ALMA

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ESO’s VLT, a powerhouse of observational astronomy, continues to push the boundaries of what can be explored. This detailed study of Abell 115 not only provides a deeper understanding of galaxy cluster mergers but also enhances knowledge of cosmic structures on vast scales, magnetic fields, and the role of dark matter in shaping the universe.

With advancements in observational techniques, researchers aim to apply these insights to other galaxy clusters, further expanding the understanding of the universe's large-scale structure. Abell 115 is just one of many systems that will be targeted by future studies, promising even more discoveries in the ever-evolving field of astrophysics.

 “According to our understanding of galaxy formation, we expect most early galaxies to be small and messy looking,” says Jacqueline Hodge, an astronomer at Leiden University, the Netherlands, and co-author of the study.

 “Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today's cosmos,” says Lucie Rowland, a doctoral student at Leiden University and first author of the study.

 “ALMA is the only telescope in existence with the sensitivity and resolution to achieve this,” says Renske Smit, a researcher at Liverpool John Moores University in the UK and also a co-author of the study.

“Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date,” says Rowland. 

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