A group that includes a University of Arizona astronomer has discovered a galaxy believed to have formed just after the Big Bang.
With stars dating back 13.5 billion years, the galaxy - which hasn't been named - was created only 200 million years after the Big Bang, astronomers believe, and may be able to tell us more about the start of the universe.
UA astronomer Eiichi Egami said his group's discovery came from a project specifically looking for extremely distant galaxies in their infancy. NASA's Hubble Space Telescope was the first to spot the galaxy, in November 2010, followed by a more-detailed view from Hawaii's W.M. Keck Observatory in January 2011. NASA's Spitzer Space Telescope also has seen the galaxy.
Immediately after the Big Bang, the universe was in the "Dark Ages," devoid of stars or galaxies and filled with hydrogen atom fog, which absorbs ultraviolet light.
As stars and galaxies formed, light from new stars pierced the fog and broke the hydrogen atoms into protons and electrons, allowing light to travel.
Knowing that the galaxy formed only 200 million years after the Big Bang suggests a population of galaxies similar to the one discovered may have assisted in the so-called "reionization." The new, hot stars formed in these galaxies would have reionized much of the hydrogen fog while developing.
The galaxy is as close to the edge of the universe that we can see, Egami said. "It's really far," he said. A beam of light can travel around the Earth 7.5 times a second, he said, noting the light from this galaxy took almost 13 billion years to travel our way. Because of the time light takes to travel, the young galaxy astronomers are seeing now is actually 13 billion years in the past.
While faint, distant galaxies aren't that unusual, there are many unique features to this one, Egami said.
Other than the little time between the galaxy's formation and when the universe started, another unique feature has to do with "gravitational lensing," Egami said.
Such distant galaxies are often hard to examine because they're too faint to be observed well. However, a massive cluster of galaxies in the foreground, with powerful gravitational force, "lensed" the background galaxy, heavily amplifying its brightness. He described it as "a huge magnifying glass floating in space."
As a result, the galaxy's apparent brightness - that is, the brightness seen by someone on Earth - is 11 times greater than without the lensing effect, he said. This allowed the team to accurately measure the galaxy's color, which is how astronomers determine a galaxy's age. It is one of the youngest galaxies ever to be seen so clearly.
Initially, the team thought the galaxy might be a "baby" galaxy in the process of forming new stars, Egami said. Instead, members learned it's a "preschooler," with stars mature enough to show the galaxy developed earlier than expected.
While the difference may not seem significant, consider Egami's analogy: Compare the universe's age to a human lifespan of, for example, 80 years.
The entire universe was only 5 years old when the light we now see left the galaxy, and the "preschool" galaxy is roughly 4, meaning in the 80-year history of the universe, it took this galaxy only the first year to form out of the hydrogen fog.
The project has another UA connection through UA undergrad Andrew Fiedler, who performed the first steps of data analysis, which included producing images and maps. Fiedler said the experience was quite different from what he usually sees as a student.
"We learn the why and how behind theories like gravitational lensing, but we don't always get connections on how they are utilized," he said.
Fiedler described the experience as "eye-opening" and said it was worth the challenge of balancing schoolwork and research.
The advancement of research thanks to accidents in nature - such as gravitational lensing - intrigues Egami.
"Nature put (galaxies) up there for no particular reason," Egami said. "But these objects make it possible for human beings to see very faint, distant galaxies, which otherwise we couldn't see."
Egami said through the advanced science, we're able to use these tools to further our knowledge.
"What fascinates me the most is the fact that nature provides such a tool for us at all," he said.
Victoria Blute is a NASA Space Grant Intern. E-mail her at vblute@azstarnet.com
