See what the blue glow is? These are the ghostly remains of the once magnificent galaxies, which have since been mixed into a space meat grinder. It may sound like a horrible Halloween movie, but it’s actually a stunning portrait of galactic evolution captured by the Hubble Space Telescope.
Abel 2744 or the Pandora Cluster consists of approximately 500 galaxies located more than 4 billion light-years from Earth. The stunning array of galaxies of various shapes and sizes is a stunner. But in this case, scientists studying the Hubble data do not admire the elegance of spiral galaxies or arcs of light curved by a gravitational lens. They focus on lost stars, abandoned to their fate in intergalactic space, released as tiny sparks after a huge galactic catastrophe that occurred billions of years ago.
The blue glow was detected by Hubble's sensitive optics and is the cosmic material evidence of galactic violence, which results in countless stars that are no longer gravitationally associated with galaxies and will forever drift alone. "The Hubble data revealing ghostly lights is an important step forward in understanding the evolution of clusters of galaxies," says Ignacio Trujillo of the Canary Institute of Astrophysics, Santa Cruz de Tenerife, Spain. "It's amazing that we found a characteristic brilliance through the use of Hubble's unique capabilities." This discovery was published in the Astrophysical Journal on October 1.
When Abel 2744 was formed, a huge number of galaxies united under a powerful mutual gravitational center. As each galaxy began to tilt toward one center, the intense gravitational forces tore the galaxies to shreds. Computer models show that this mechanism probably occurs in large clusters of galaxies. In the case of Abel 2744, over 200 billion stars were scattered throughout the cluster.
“These results are in good agreement with what was predicted in computer models,” said lead author Mirei Montes, also from the Canary Institute of Astrophysics.
Interestingly, Hubble was not specifically used to study this ghostly glow. As part of the Frontier Fields project, Hubble's sensitive optics are used to study large galactic clusters, such as Abel 2744, to study the phenomenon of gravitational lensing. The arcs of light in this image are an example of lensing artifacts, when the light from galactic clusters is deformed due to the enormous gravity of the cluster. But for the team of Montes, this glow coming from the ancient galactic clusters is of particular interest.
Since the Frontier Fields project continues to use galactic clusters as natural lenses to explore the farthest corners of space, researchers will continue to observe these luminous clusters, getting a better idea of how these gravitational giants were formed.