Regular readers know I love me my gamma-ray bursts: the most titanic and violent explosions the Universe is capable of producing. If one were to occur within a few thousand light years of the Earth, it would sterilize our planet down to the base of the crust.
Happily for us, all GRBs happen very far away. And on September 13th, NASA’s Swift satellite saw what has turned out to be the most distant GRB ever detected: the light from the massive star that died and created the burst traveled 12.8 billion light years to reach us.
|A combination of Swift’s ultraviolet and X-ray views of GRB 080913, the most distant burst ever seen so far.|
That means the Universe was only a little over 800 million years old when the star died, which in turn means the star itself was among the first in the Universe to be born; the first stars were formed about 400 million years earlier. The star probably only lived a few scant million years before detonating, catastrophically tearing itself to shreds at the end of its life, and releasing as much energy in a few seconds as the Sun will over its entire 10 billion year lifetime. For a few seconds the dying star was the single brightest object in the Universe, but over the intervening eons as its roar traveled across the cosmos it faded to whisper, eroded by its travel, literally fighting against the expansion of space itself.
Almost 13 billion years after the event, that whisper was detected by Swift, and the coordinates quickly relayed to the ground, where follow-up observations were rapidly produced. Within hours, spectra taken using a monster 8-meter telescope in Chile revealed the terrible distance to the burst (for those who like details, the redshift of the burst was measured at a record-breaking 6.7). This shattered the previous record holder, which was 70 million light years closer to us when it blew up.
The burst was so distant that the optical light emitted by the explosion had been redshifted into the infrared, and even then it was amazingly faint, less than a millionth as bright as what our eyes can detect (even if we could see in the IR, which we can’t). They say time heals all wounds, but sometimes vast distances can do the trick as well.
Probing ever further into the Universe is a rich field for astronomy. We learn more about the behavior of objects back then; how they lived, how they died, and in what environment they spent the intervening years. The heavy elements created in those far-distant explosions eventually became us: the iron in your blood and the calcium in your teeth were created in supernovae and gamma-ray burst explosions billions of years ago. When you look at the picture of that terribly-removed explosion, remember that you’re almost literally looking in a mirror.
And need I remind you? Chapter 4 of Death from the Skies! has everything you’ve ever wanted to know about GRBs in it, including what would happen if one were to go off too close to us for comfort.