Last March our planet looked straight down the barrel when one of the universe's most deadly kinds of stellar artillery fired — and we lived to tell about it.
The March 19 cosmic cannon was a jet of powerful gamma rays that shot out matter at speeds just a hair shy of the universal speed limit — that of light.
The explosion, which occurred not far from the handle of the Big Dipper, was even more remarkable because it was accompanied by enough visible light to be seen briefly with unaided human eyes. That's despite the fact that the dying mega-star that created the blast was in another galaxy, a whopping 7.5 billion light-years away.
"It definitely broke some records," said astronomer Dieter Hartmann of Clemson University in South Carolina. "The luminosity was a million times that of the whole galaxy, which is astounding."
It was so bright, in fact, that at first one of its discoverers thought something was wrong, said Judith Racusin, a graduate student at Pennsylvania State University. Racusin is the lead author of a paper on the discovery in the Sept. 11 issue of the journal Nature.
The gamma ray burst, dubbed GRB 080319B, was detected by NASA's Swift satellite, which is equipped specifically to spot such events quickly. Both Swift's X-Ray Telescope and its UltraViolet/Optical Telescope were blinded by the unusually bright blast.
Ensuing observations around the world with other satellites and ground-based telescopes collected an unprecedented amount of data from across the electromagnetic spectrum. No fewer than 92 researchers have combined their work to publish the Nature paper.
"We really hit the jackpot," said Swift principal investigator Neil Gehrels at NASA's Goddard Space Flight Center.
"We've been waiting a long time for this one," agreed Grigory Beskin of Russia's Special Astrophysical Observatory.
The plethora of data on GRB 080319B collected around the world has now been combined to produce the best picture yet of the incredibly violent stellar event.
It has also revealed that Earth was within range of a very narrow, ultra-fast central beam of the jet that shot out of the star, not even a half of a degree across.
"It's unbelievable opening angle of 0.4 degrees," said Hartmann of the inner jet which hit Earth. "It allows us to look right at it."
Rarely are these jets so well-aimed at Earth, and it's only the vast distance of their origins that keeps them from wreaking havoc on Earth's climate.
"If it happened in our galaxy we would actually be in considerable trouble," said Swift team leader David Burrows of Pennsylvania State University. It could cause chemical changes in our atmosphere that could result in rapid global winters and mass extinction events, he said.
The event also allows for new measurements of elements in intergalactic space between Earth and the blast, Hartmann explained, something few objects are bright enough to do.
Gamma ray bursts are the brightest eruptions in the universe, believed to be caused by very massive stars running out of fuel and imploding.
Exactly how the jets of nearly light-speed particles are created is still somewhat of a mystery. But it is clear these jets slam into material already shed by the star and light it up, creating an afterglow that can last for months.