The Hubble Space Telescope of NASA has recently spotted ghostly light coming from stars that were ejected from within ancient galaxies.
The ancient galaxies died several billions of years ago due to intense gravitational pulls, with the incident happening about 4 billion light years from the Earth within Pandora's Cluster.
Pandora's Cluster, which is also named the Abell 2744, is a massive group of almost 500 galaxies. The stars from which the ghostly light came from are not anymore part of any one of these galaxies, drifting between the galaxies within the cluster.
Astronomers operating the Hubble used their observations on the light from the ejected stars to assemble forensic evidence which suggests that as many as six galaxies were shredded to pieces within Pandora's cluster over a period of 6 billion years.
Utilizing computer modeling techniques, astronomers have estimated that the galaxies from which the ejected stars originally came from were about the size of our own Milky Way galaxy. These galaxies were likely ripped apart when they entered the center of Pandora's Cluster, where opposing gravitational forces are at their strongest.
A hypothesis by astronomers states that light coming from the ejected stars of the doomed galaxies should be picked up by instruments such as the Hubble once the galaxies have disbanded. However, the glow of the stars looks very faint, which makes it difficult for astronomers to identify if the stars are the ejected and drifting stars.
"The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters," said Ignacio Trujillo from The Instituto de Astrofísica de Canarias in Spain.
The astronomers estimate that about 10 percent of the brightness of Pandora's Cluster is composed of the light coming from the outcast stars within the cluster, which is thought to number around 200 billion.
The very faint light of the stars are best seen and at their brightest at wavelengths of light that near infrared categories. As such, observing the stars can only be done with the Hubble, which has infrared sensitivity to very faint light.
Measurements made by the Hubble also show that the ghostly stars are bountiful in the heavier elements such as carbon, oxygen and nitrogen. This data points to the fact that the stars are second-generation or third-generation stars.
The team of Montes utilized the data that Hubble recorded from Pandora's Cluster in the Frontier Fields program, which is a three-year program to observe certain massive clusters of galaxies.
The program will involve five more galaxy clusters, and Montes and his team are planning to search for the ghostly light from these clusters as well.
