Free Astronomy Magazine March-April 2023

MARCH-APRIL 2023 tion for astronomers has been: how did the stars get so scattered throughout the cluster in the first place? Several competing theories in- clude the possibility that the stars were stripped out of a cluster’s galax- ies, or they were tossed around after mergers of galaxies, or they were present early in a cluster’s formative years many billions of years ago. A recent infrared survey from NASA’s Hubble Space Telescope, which looked for this so-called “in- tracluster light” sheds new light on I n giant clusters of hundreds or thousands of galaxies, innumer- able stars wander among the gal- axies like lost souls, emitting a ghostly haze of light. These stars are not gravitationally tied to any one galaxy in a cluster. The nagging ques- Mysterious “ghost” stars wandering around for billions of years by NASA/ESA Bethany Downer