Hubble telescope glimpses universe's earliest galaxies
New Hubble telescope images provide a look at the cosmos when it was just 600 to 800 million years old. Galaxies from this period might have helped transform the universe from dark to light.
The recently refurbished Hubble Space Telescope has drawn back a curtain on a group of galaxies that are the earliest the universe has yet produced.Skip to next paragraph
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The galaxies, hot, small, and blue, appear as faint patches of fuzz in the image Hubble took of a patch of sky over four days last August, peering back into a period when the cosmos was only 600 million to 800 million years old - less than one-twentieth of its current age - and a little more than 10 percent of its current size.
In addition these early galaxies, the international team of scientists reporting the results Tuesday say their "ultra-deep field" image contains at least three galaxy candidates that existed when the universe was some 500 million years old. They remain candidates because they are too faint for detailed study.
The discoveries help mark a watershed in modern astronomy and cosmology, according to John Grunsfeld, one of the astronauts who helped repair and refurbish Hubble last May and who has just been appointed as deputy director of the Space Telescope Science Institute in Baltimore.
Just a hundred years ago, astronomers such as Edwin Hubble were debating the nature of "nebula" they saw in the night sky – cloudy patches of light that we now know as galaxies. At that time, "we didn't know we lived in a universe where we could see the beginning of star formation and galaxies," Mr. Grunsfeld said at a briefing at the winter meeting of the American Astronomical Society in Washington, D.C.
"This is a remarkable time,” he said, thanks to some remarkable tools that are helping push the frontiers of astronomy.
After the Big Bang
Interest in the universe’s first billion years is running high because it marks a critical phase in the universe’s evolution.
The universe is thought to have begun some 13.7 billion years ago with an energetic burst known as the Big Bang. As the universe expanded and cooled, the building blocks of matter began to distill from the seething soup of higher-energy particles the Big Bang created. The universe cooled to the point where it was populated by run-of-the-mill molecules. Roughly 75 percent of the matter in the universe was hydrogen, 25 percent helium, along with traces of a small handful of other elements. No stars shone. No galaxies pirouetted.
At some point between 100 million and 1 billion years after the Big Bang, cosmologists calculate, the universe slowly began to switch on the lights. The cosmos shifted from the cold and opaque aftermath of the Big Bang to a transparent universe filled with the dazzling display of stars, galaxies, galaxy clusters, and super clusters that humans gaze on today.
"We don't know who pulled the trigger" on this period, known as re-ionization, says Rogier Windhorst, a cosmologist at Arizona State University in Tempe, Ariz., and a member of the Hubble team.