NASA's Hubble Space Telescope has found the long-suspected underlying population of galaxies, which produced the bulk of new stars during the universe's early years.
Abell 2744 has the smallest, faintest, and most numerous galaxies ever seen in the remote universe, captured by Hubble deep exposures taken in ultraviolet light.
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 typically detected in previous deep-field surveys of the early universe.
These galaxies would normally be too faint for Hubble to see. To detect them, astronomers teamed Hubble with a natural zoom lens in space, produced by the gravity of a giant foreground galaxy cluster, Abell 1689.
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.
Siana's team believes it has completed the census of galaxies at an epoch when the universe was roughly 3.4 billion years old.
The study has been published online in The Astrophysical Journal.
