The brightest explosion ever seen sent a blast of gamma rays directly towards the earth, according to a paper in this week’s Nature.

Caused by a dying star halfway back to the big bang, the gamma ray burst was visible on Earth for 40 seconds to anyone who looked to the right point in the sky in March 2008.

“It definitely broke some records,” says Dieter Hartmann of Clemson University in South Carolina, who is not an author on the paper (MSNBC). “The luminosity was a million times that of the whole galaxy, which is astounding.”

Luckily for researchers the narrow beam of rays was pointed pretty much directly at Earth, allowing them to study it in considerable detail. “It’s like shooting a gun with a deadly laser beam embedded within a lethal spray of buckshot,” says Sky and Telescope.

In a News & Views article about the burst Jonathan Grindlay notes that the optical emission of the burst was 100 brighter than the previous record holder. Knowledge of this burst and its dual-jet nature – an inner beam just 0.4 degrees wide sheathed inside another wider beam about 8 degrees wide – may challenge our current understanding of gamma ray bursts.

If such dual jets are common the bursts may be 10 to 100 times more common than we thought, says Grindlay. We just haven’t seen them because they’re not pointed at us.

Reuters takes the apocalypse angle:

If a similar gamma ray burst occurred within our own Milky Way galaxy a few thousand light-years away instead of billions of light years, it might have disrupted Earth’s atmosphere and caused a “nuclear winter” effect that could have threatened life on our planet, the researchers said.

“We were not in danger,” Paul O’Brien of the University of Leicester in Britain, one of the scientists, said by e-mail. “Although it is extremely powerful, only a tiny fraction of the radiation reached the Earth.”

Image: ESA