The Hubble space telescope continues to reveal more secrets about our universe.
A team of scientists from the University of California Riverside are using the space telescope to observe galaxy candidates around Abell 2744.
Abell 2744 is a giant galaxy cluster, situated in the Sculptor constellation, that was derived from the simultaneous collision of multiple smaller galaxy clusters – an incident that transpired over a span of 350 million years. The region is nicknamed Pandora’s Cluster.
The 58 young, diminutive galaxies spied by Hubble were photographed as they appeared more than 10 billion years ago, during the heyday of star birth. The newly discovered galaxies are 100 times more numerous than their more massive cousins. But they are 100 times fainter than galaxies detected in previous deep-field surveys of the early universe.
These galaxies would normally be too faint for Hubble to see. But the astronomers were able to detect them by teaming Hubble with a natural zoom lens in space, produced by the gravity of Abell 1689, a giant foreground galaxy cluster. The cluster is so massive that it magnifies the light from faraway galaxies behind it due to a phenomenon called gravitational lensing, where the curvature of space acts like a giant funhouse mirror to stretch and brighten distant objects.
“There’s always been a concern that we’ve only found the brightest of the distant galaxies,” said study leader Brian Siana, an assistant professor of physics and astronomy. “The bright galaxies, however, represent the tip of the iceberg. We believe most of the stars forming in the early universe are occurring in galaxies we normally can’t see at all. Now we have found those ‘unseen’ galaxies, and we’re really confident that we’re seeing the rest of the iceberg.”
Siana’s team believes it has completed the census of galaxies at an epoch when the universe was roughly 3.4 billion years old. If this sample of galaxies is representative of the entire population at this early time, then the majority of new stars formed in these small galaxies.
“Though these galaxies are very faint, their increased numbers means that they account for the majority of star formation during this epoch,” said team member Anahita Alavi, a Ph.D. graduate student in Siana’s lab, and the first author of the research paper.