Astronomers have observed an ancient galaxy in the depths of outer space after catching a glimpse of light produced by an exploding star. When the dying star exploded more than 12 billion years ago, it so with so much force that the light it created was millions of times brighter than the the rest of the light in its galaxy. Light from that explosion has traveled from so far away that when the explosion occurred, Earth had not even formed yet.
Using a variety of telescopes analyze the light, astronomers have learned about an ancient galaxy which would have otherwise been too small and faint to pick out, had the explosion not occurred.
"This star lived at a very interesting time, the so-called dark ages just a billion years after the Big Bang," said Ryan Chornock of the Harvard-Smithsonian Center for Astrophysics (CfA) and lead author of a study on the new find.
"In a sense, we're forensic scientists investigating the death of a star and the life of a galaxy in the earliest phases of cosmic time," he added.
When stars explode they unleash huge amounts of gamma rays. These gamma-ray bursts (GRBs) are the brightest electromagnetic events known to occur in the universe. The GRB that occurred in this ancient galaxy was notably long, about four minutes, the researchers report.
The GRB was first detected by NASA's Swift spacecraft on June 6, and the observation was quickly followed up on by Chomock and his colleagues at the MMT Telescope in Arizona and the Gemini North telescope in Hawaii. At a redshift of 5.9, or a distance of 12.7 billion light-years, this GRB is one of the most distant ever found.
"We were able to get right on target in a matter of hours," Chornock said. "That speed was crucial in detecting and studying the afterglow."
Afterglow refers to the light produced as the GRB passes though surrounding gasses, heating the gas and causing it to glow.
"As the afterglow's light travels through the dead star's host galaxy, it passes through clouds of interstellar gas," the researchers report. "Chemical elements within those clouds absorb light at certain wavelengths, leaving 'fingerprints.' By splitting the light into a rainbow spectrum, astronomers can study those fingerprints and learn what gases the distant galaxy contained."
By studying the gasses an the fingerprints, the astronomers can deduce the chemical elements present in the galaxy. They determined that carbon and oxygen could not have existed in the ancient galaxy, and therefore, life as we know it also did could not have existed in the galaxy either. Chornock and his colleagues found that the GRB galaxy contained only about one-tenth of the metals in our solar system.
"At the time this star died, the universe was still getting ready for life. It didn't have life yet, but was building the required elements," Chornock said.
Chornock and his colleagues' research is available online and is scheduled for publication in the September issue of The Astrophysical Journal.