Behold, the light of a gamma-ray burst that took place more than 13 billion years ago!
As most of you are aware, the universe is expanding at an ever-increasing speed, which in turn, pushes all galaxies farther away from us. Ultimately, this will result in these galaxies receding so far away, to the point that some of them eventually disappear forever, traveling too fast (located too far away) for their light to ever reach us. However, many of the galaxies that are now too far away were once much closer, offering us an opportunity to study distant, ancient galaxies as they appeared long before our planet was conceived.
As such, astronomers were recently able to detect a destructive event from one such galaxy, located 12.7 billion light-years away. Meaning we are observing the galaxy as it appeared almost 13 billion years ago; basically when the universe was still in diapers, more or less. The galaxy is generally too far away (and too red-shifted as a result of the universe’s expansion) for us to be capable of observing closely, but we were able to detect the galaxy as it was illuminated by a gamma-ray burst, one of the most energetic celestial explosions. This high energy burst of gamma-rays was cataloged by astronomers as GRB 130606A.
GRB 130606A lasted almost four minutes in all, classifying it as a long-term gamma-ray burst, which are formed when massive stars go supernova (although GRBs can ignite in other ways). During this four minute window of time, the gamma-ray burst became millions of times brighter than the host galaxy, effectively building a huge, flashing neon sign that says “LOOK AT ME!”.
After they occur (and believe me when I tell you that they are quite easy to spot), they generate an afterglow. This effect is produced as the jets of gas emitted by the narrow beam slams into gas in the interstellar medium, causing it to heat up exponentially until it glows. Astronomers are then able to take a look at the spectrum of light emitted from the afterglow. Breaking this light down into its constituent parts allows researchers to determine exactly which elements are present and the concentration of each. With GRB 130606A, it was discovered that the host galaxy once contained only 1/10th of the heavy elements found in our solar system. This did not come unexpected to astronomers, as the galaxy is surely filled mostly with first generation stars. In this early epoch of the universe, these first stars coalesced in a period of time before heavy elements were seeded through space thanks to supernovae.
“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,” says Ryan Chornock, the paper’s lead author.