Astronomers have captured an unprecedented image of the galaxy cluster Abell 2255, revealing intricate, radio-emitting tendrils that stretch for over 360,000 light-years across intergalactic space. Located approximately 800 million light-years from Earth, this sprawling cluster contains up to 500 galaxies, many of which are interacting or merging.
A New Window Into Ancient Radio Galaxies
The research focused on radio galaxies, a type of galaxy dominated by supermassive black holes that eject jets of matter at near-light speeds. These galaxies emit powerful radio waves, often forming long tails as the jets interact with surrounding cosmic material. In the case of Abell 2255, the VLBI mode of LOFAR enabled scientists to observe these features with an angular resolution as sharp as 0.3 arcseconds over 56 hours of exposure at 144 MHz. The result: highly detailed filaments extending three times the width of the Milky Way, yet thinner than one-tenth of its diameter.
These mysterious filaments are likely shaped by turbulent forces within the cluster itself. The study team, believe that they originate inside the radio galaxies and are stretched by chaotic motions throughout Abell 2255. Over time, these threads of radio emission are expected to blend into the intergalactic medium, the vast and diffuse collection of gas and dust that exists between galaxies.
Unveiling The Tailed Radio Galaxy And Its Cosmic Cousins
Among the cluster’s most striking features is the Original Tailed Radio Galaxy, a unique object with a tangled and filament-rich tail unlike anything seen before. This galaxy’s structure offers a new perspective on how black hole jets evolve and interact with their environment. The LOFAR data also revealed previously unseen detail in other oddly-shaped galaxies within Abell 2255, including the Goldfish, the Beaver, and the Embryo. Each one trails its own radio “tail” extending more than 200,000 light-years behind it, shaped by the extreme conditions inside the cluster.
“We calibrated 56 hours of observations, divided into nightly sessions of about 8 hours each,” explained Emanuele De Rubeis, a researcher at the University of Bologna. “The raw data from each night is about 4 terabytes, but after calibration, the volume increases to 18 to 20 terabytes for a total of about 140 terabytes overall.” According to De Rubeis, processing just one night’s worth of data to generate high-quality images of the sources could take up to a month.
Exploring The Cluster’s Magnetic Landscape
The new findings offer a rare opportunity to explore not just the galaxies themselves but also the magnetic properties of the gas that fills the space between them. “These results open the way to new perspectives for the study not only of radio galaxies but also of the properties of the gas that permeates galaxy clusters,” said Marco Bond, a researcher at the National Institute for Astrophysics (INAF).
Modern radio telescopes like LOFAR and upcoming SKA (Square Kilometre Array) precursors are changing how astronomers observe such diffuse structures. Their sensitivity and resolution allow researchers to detect phenomena that were once too faint or complex to observe, revealing how galactic jets evolve, how they transfer energy into surrounding space, and how cosmic magnetism is distributed across vast distances.
