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New insights into star-forming giant galaxy cluster

Galaxy clusters, huge conglomerations of galaxies, hot gas, and dark matter, are the largest structures in the Universe held together by gravity. But they are generally poor at producing new stars in their centres.

The galaxy cluster SPT-CLJ2344-4243, nicknamed the Phoenix Cluster, however, bucks the trend.

Scientists already knew the cluster featured the highest rate of cooling hot gas and star formation ever seen in the centre of a galaxy cluster, and that it is the most powerful producer of X-rays of all known clusters.

Now new data from observations at X-ray, ultraviolet, and optical wavelengths by NASA’s Chandra X-ray Observatory, the Hubble Space Telescope, and the Clay-Magellan telescope in Chile, are helping astronomers better understand how this may be happening. 

NASA explains:

Clay-Magellan’s optical data reveal narrow filaments from the center of the cluster where stars are forming. These massive cosmic threads of gas and dust, most of which had never been detected before, extend for 160,000 to 330,000 lights years. This is longer than the entire breadth of the Milky Way galaxy, making them the most extensive filaments ever seen in a galaxy cluster.

They surround large regions with greatly reduced X-ray emission in the hot gas. These regions can be seen as dark patches surrounded by the blue in the composite image above, which shows the Chandra X-ray data in blue and optical data from the Hubble Space Telescope (red, green, and blue).

Astronomers think that the X-ray cavities were carved out of the surrounding gas by powerful jets of high-energy particles emanating from near a supermassive black hole in the central galaxy of the cluster. As matter swirls toward a black hole, an enormous amount of gravitational energy is released. Combined radio and X-ray observations of supermassive black holes in other galaxy clusters have shown that a significant fraction of this energy is released as jets of outbursts that can last millions of years. The observed size of the X-ray cavities indicates that the outburst that produced the cavities in SPT-CLJ2344-4243  SPT- CLJ2344-4243 was one of the most energetic such events ever recorded.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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