Galaxy cluster collision revives “radio phoenix”

The collision of two massive galaxy clusters 1.6 billion light years from Earth revived a radio source in a fading cloud of electrons, creating a “radio phoenix.” The phenomenon was recorded by a team of astronomers including William Dawson of the UC Davis physics department and Lawrence Livermore National Laboratory.

Composite image of colliding galaxy cluster Abell 1033 combines X-ray data from Chandra (pink) along with radio data (green) and optical data that reveals the density of the galaxies (blue). (NASA)

Composite image of colliding galaxy cluster Abell 1033 combines X-ray data from Chandra (pink) along with radio data (green) and optical data that reveals the density of the galaxies (blue). (Chandra X-ray Observatory)

According to a news release from the Chandra X-ray observatory,

Astronomers think that the supermassive black hole close to the center of Abell 1033 erupted in the past. Streams of high-energy electrons filled a region hundreds of thousands of light years across and produced a cloud of bright radio emission. This cloud faded over a period of millions of years as the electrons lost energy and the cloud expanded.

The radio phoenix emerged when another cluster of galaxies slammed into the original cluster, sending shock waves through the system. These shock waves, similar to sonic booms produced by supersonic jets, passed through the dormant cloud of electrons. The shock waves compressed the cloud and re-energized the electrons, which caused the cloud to once again shine at radio frequencies.

The “phoenix” can be seen as the bright white splotch in the center of this image. X-rays are shown in pink and dark matter in blue.

Galaxy clusters are the most massive objects in the universe held together by gravity. Understanding how they grow is important for understanding how the universe has evolved over time.

Previously, Dawson and colleagues observed how the collision of another pair of galaxy clusters caused a new burst of star formation in a dormant area.

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