The Bullet Cluster, a cosmic collision between two massive galaxy clusters, has been observed in unprecedented detail using NASA’s James Webb Space Telescope (Webb). Located nearly 3.8 billion light-years away from Earth, this phenomenon is one of the most iconic scenes in the universe.
Two galaxy clusters collided over several billion years ago, resulting in the formation of a new cluster and a massive amount of hot gas that was heated by shockwaves. The Bullet Cluster is now considered one of the hottest-known galaxy clusters, with temperatures reaching millions of degrees. This heat released X-ray emissions detectable by telescopes like Chandra.
Astronomers used Webb to refine the mass of the Bullet Cluster, which is primarily composed of dark matter. Dark matter makes up most of the cluster’s mass and distorts light from distant objects due to its gravitational effect. By studying the distribution of hot gas in the cluster, scientists gained valuable insights into the behavior of dark matter.
The Bullet Cluster consists of two main components: a smaller sub-cluster called the Bullet and the larger one it collided with. Webb observations revealed extremely detailed images of galaxy members, as well as faint galaxies beyond the cluster. The instrument’s ability to study the distribution of hot gas helped researchers map the location of dark matter in the cluster.
“Webb’s images dramatically improve what we can measure in this scene — including pinpointing the position of invisible particles known as dark matter,” said Kyle Finner, a co-author and assistant scientist at Caltech. Dark matter plays a crucial role in the Bullet Cluster’s hot gas clouds, light from distant galaxies, and gravitational lensing.
The Webb view also allows scientists to study the distant galaxies “behind” the cluster in great detail. Distorted images reveal clues about the distribution of dark matter within the lens. By studying these distortions, researchers can infer the location and behavior of dark matter in the cluster.
The Bullet Cluster’s gravitational lens reveals thousands of distant galaxies whose light is “smeared” and distorted by the gravitational effect of dark matter. This allows astronomers to map the distribution of dark matter that makes up the cluster.
The new observations using Webb provide stronger limits on the behavior of dark matter particles, revealing that they act independently of each other beyond gravitational attraction. The findings shed new light on the mysterious nature of dark matter and its role in the Bullet Cluster.
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