Astronomers using NASA's Hubble Space Telescope as a "time machine" have obtained the clearest views yet of distant galaxies that existed when the universe was a fraction of its current age.
A series of remarkable pictures, spanning the life history of the cosmos, are providing the first clues to the life history of galaxies. The Hubble results suggest that elliptical galaxies developed remarkably quickly into their present shapes. However, spiral galaxies that existed in large clusters evolved over a much longer period the majority being built and then torn apart by dynamic processes in a restless universe.
Astronomers, surprised and enthusiastic about these preliminary findings, anticipate that Hubble's observations will lead to a better understanding of the origin, evolution, and eventual fate of the universe. The Hubble observations challenge those estimates for the age of the universe that do not allow enough time for the galaxies to form and evolve to the maturity seen at an early epoch by Space Telescope.
"These unexpected results are likely to have a large influence on our cosmological models and theories of galaxy formation," says Duccio Macchetto of the European Space Agency and the Space Telescope Science Institute (STScI). "These Hubble telescope images are sufficient to provide a first determination of the properties of these very young and distant galaxies."
"This is compelling, direct visual evidence that the universe is truly changing as it ages, as the Big Bang model insists," emphasizes Alan Dressler of the Carnegie Institutions, Washington, D.C. "Though much of the quantitative work can be done best with large Earth-bound telescopes, Hubble Space Telescope is providing our first view of the actual forms and shapes of galaxies when they were young."
"These initial results are surprising," adds Mauro Giavalisco (STScI). "Hubble is giving us, for the first time, a chance to study in great detail the properties of very young galaxies and understand the mechanisms of their formation."
A series of long exposures, taken by separate teams led by Macchetto, Dressler, and Mark Dickinson (STScI) trace galaxy evolution in rich clusters that existed when the universe was approximately one-tenth, one-third, and two-thirds its present age. Their key findings:
Scientists identified the long-sought population of primeval galaxies that began to form less than one billion years after the Big Bang.
One of the deepest images ever taken of the universe reveals a "cosmic zoo" of bizarre fragmentary objects in a remote cluster that are the likely ancestors of our Milky Way Galaxy.
A series of pictures, showing galaxies at different epochs, offers the most direct evidence to date for dynamic galaxy evolution driven by explosive bursts of star formation, galaxy collisions, and other interactions, which ultimately created and then destroyed many spiral galaxies that inhabited rich clusters.
Postcards from Edge of Space and Time
The researchers used Hubble as a powerful "time machine" for probing the dim past. The astronomical equivalent of digging through geologic strata on Earth, Hubble peers across a large volume of the observable universe and resolves thousands of galaxies from five to twelve billion light-years away. Because their light has taken billions of years to cross the expanding universe, these distant galaxies are "fossil evidence," encoded in starlight, of events that happened long ago.
These long-exposure Hubble images will help test and verify ideas about galaxy evolution based on several decades of conjecture, theoretical modeling, and ground-based observation. Ground-based observations have not been able to establish which of several competing theories best describe how galaxies formed and evolved in the early universe.
Though the largest ground-based telescopes can detect objects at great distances, only Hubble can reveal the shapes of these remote objects by resolving structures a fraction of the size of our Milky Way Galaxy. This is allowing astronomers, for the first time, to discriminate among various types of distant galaxies and trace their evolution. Like watching individual frames of a motion picture, the Hubble pictures reveal the emergence of structure in the infant universe, and the subsequent dynamic stages of galaxy evolution.
Now that Hubble has clearly shown that it is an exquisite time machine for seeking our cosmic "roots," astronomers are anxious to push back the frontiers of time and space even further. "Our goal now is to look back further than twelve billion years to see what we are sure will be even more dramatic evidence of galaxies in formation," says Dressler.
Ray Villard, STScI
Duccio Macchetto, STScI
Alan Dressler, Carnegie Institutions of Washington
Mark Dickinson, STScI