Hubble Space Telescope Spots Eerie, Ghostly Light of Stars from Dead Galaxies

Just in time for Halloween, NASA's Hubble Space Telescope has captured the ghostly glow of stars ejected from ancient galaxies that were ripped apart several billion years ago. Inside an immense collection of nearly 500 galaxies nicknamed "Pandora's Cluster," scientists can see the light coming from galaxies that are now dead.

The scattered stars are no longer bound to any one galaxy. Instead, they drift freely between the galaxies in the cluster, which is formally called Abell 2744. The new data from Hubble actually suggests that as many as six galaxies were torn to pieces in the cluster over a period of six billion years.

"The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters," said Ignacia Trujillo, one of the researchers, in a news release. "It is also amazingly beautiful in that we found the telltale glow by utilizing Hubble's unique capabilities."

The combined light of the 200 billion outcast stars actually contributes to about 10 percent of the cluster's brightness. Many of the now-dead galaxies were likely as big as our Milky Way, and would have been pulled apart like taffy if they plunged through the center of the galaxy where gravitational tidal forces are strongest.

Hubble measurements were able to tell that the phantom stars are rich in heavier elements like oxygen, carbon and nitrogen. This means that the scattered stars are second- or third-generation stars that were enriched with the elements forged in the hearts of first-generation stars.

The findings reveal a bit more about this cluster and shed more light on the origins of these ghostly stars that are the leftovers of dead galaxies. This, in turn, tells scientists a bit more about galaxy and cluster evolution.