Halloween is here, and NASA has given the All Hallows’ Eve a new cosmic twist. The space agency has spotted a “ghost light” ejected from dead galaxies that were ripped apart gravitationally billions of years ago. The multi-galaxy massacre happened inside the “Pandora’s Cluster,” which is also known as Abell 2744. Pandora’s Cluster is a collection of more than 500 galaxies.
NASA scientists used Hubble to observe the ghost light
The mayhem took place about 4 billion light years away from the Earth, over a period of 6 billion years. Six galaxies about the size of the Milky Way died in the celestial bloodbath, NASA said. Now, the scattered stars are not bound to any specific galaxy. Instead, they wander freely between galaxies in Abel 2744. NASA scientists were able to observe the ghost light from these orphaned stars with the help of Hubble Space Telescope.
How did those galaxies die? NASA said in a statement that the doomed galaxies were “pulled apart like taffy” when they passed through the center of the cluster where gravity is strongest. Scientists have long believed that ghost light from scattered stars should be detectable. But they hypothesized that “intracluster” glow of stars was extremely faint, so it would be difficult to identify.
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But Hubble’s infra-red sensitivity to dim light made it possible because faint stars appear the brightest at near-infrared wavelengths of light. Ignacio Trujillo of The Instituto de Astrofísica de Canarias (IAC) in Spain said that the observations will help scientists understand the evolution of galaxy clusters. NASA scientists estimate that the combined light from over 200 billion such outcast stars make up about 10% of Abell 2744’s brightness.
Abell 2744 a target in NASA’s Frontier Fields program
NASA researchers also determined that these “phantom stars” are very rich in heavier elements such as carbon, oxygen and nitrogen. It indicates that the scattered stars are second- or third-generation stars. Pandora’s cluster is also a target in NASA’s Frontier Fields program. Under the three-year program, scientists will be studying select galaxy clusters to help understand the remote universe.