Phoenix Cluster

The Phoenix Cluster (SPT-CL J2344-4243) is a very large group of galaxies called a galaxy cluster. It is found in the southern sky, in the area of the constellation called Phoenix. Astronomers first found this cluster in 2010 using a special telescope at the South Pole called the South Pole Telescope. They used a method called the Sunyaev–Zeldovich effect to look at a large part of the sky.

The Phoenix Cluster is one of the biggest galaxy clusters known. It has a mass about 2,000,000,000,000 times the size of our Sun, written as 2×10¹⁵ M_☉. It shines very brightly in a type of energy called X-rays, more than any other big galaxy cluster found so far. It is very far away, about 8.61 billion light-years from Earth.

Scientists have identified around 42 galaxies in the Phoenix Cluster using a database called SIMBAD. However, they think there might be as many as 1,000 galaxies there in total, hidden among the bright lights and gases.

Discovery

The Phoenix Cluster was first found during a big sky survey done by the South Pole Telescope in Antarctica. This cluster is one of 26 galaxy clusters spotted in the survey. Twelve of these clusters, including the Phoenix Cluster, were newly discovered. Scientists noted that the Phoenix Cluster shines very brightly in X-rays, more than any other cluster known at that time. Near the center of the cluster, they also found a special type of galaxy called a type-2 Seyfert galaxy, later named Phoenix A.

Characteristics

The Phoenix Cluster is one of the most important objects of its type because of its extreme properties. It has an extremely strong cooling flow, which means that material in the cluster is cooling very quickly. This cooling flow is one of the highest ever observed in the middle of a galaxy cluster.

The Phoenix Cluster also has the highest X-ray luminosity compared to other clusters. This means it gives off more X-ray light than any other known massive cluster. The central galaxy in the Phoenix Cluster, named Phoenix A, is forming new stars at a very fast rate.

Components

The central galaxy of the Phoenix Cluster, called Phoenix A, is a very large and active galaxy. It has a very bright center, called an active galactic nucleus, which is powered by a supermassive black hole. This galaxy is one of the largest known, stretching about 360,300 light-years across.

Phoenix A contains a huge amount of hot gas and is forming new stars at an amazing rate—about 740 times the mass of our Sun every year. This is much faster than in other big clusters of galaxies. The black hole at its center might be one of the biggest ever found, possibly weighing as much as 100 billion times the mass of our Sun. If it were placed where our Sun is, its edge would reach far beyond the planet Pluto.

JWST observations

In 2025, NASA's James Webb Space Telescope (JWST) made an important discovery about the Phoenix Cluster. It found a special kind of gas that is just the right temperature to help new stars form quickly. This gas is much hotter than the cool gas in the cluster but not as hot as the very warm gas, making it a unique find that helps scientists understand how stars are born in big groups of galaxies.