Monday, April 07, 2008

Battlestar Galactigeek

If back very early on March 19, at about 2:12 AM Eastern Time, in fact, you happened to be outside looking at the night sky, and if you happened to have very good viewing conditions, and if you happened to be looking toward the constellation Bo├Âtes, perhaps looking for Arcturus (remember to "arc to Arcturus"), and if you didn't close your eyes at the wrong moment, you might have seen a brief flash of light.

You likely would have been surprised. You likely would have wondered what it was. You likely would not have guessed.

What you would have seen was a gamma ray burst from the most distant object ever to be seen with the naked eye: Some 7.5 billion light years away, more than halfway across the visible universe.
"It was a whopper," says [NASA] Swift [satellite] principal investigator Neil Gehrels of NASA's Goddard Space Flight Center. "This blows away every gamma ray burst we've seen so far." ...

Most gamma ray bursts occur when massive stars run out of nuclear fuel. Their cores collapse to form black holes or neutron stars, releasing an intense burst of high-energy gamma rays and ejecting particle jets that rip through space at nearly the speed of light. When the jets plow into surrounding interstellar clouds, they heat the gas to incandescent visibility. It is this gaseous "afterglow" which was visible to the human eye on March 19th.

GRB 080319B's afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The most distant previous object that could have been seen by the naked eye is the nearby galaxy M33, a relatively short 2.9 million light-years from Earth.
So this was over two and a-half times further away. Scientists aren't sure why this particular event was so bright; it could have been intrinsically brighter or perhaps its energy release was in a narrow stream pointed directly at Earth.

You can see an animated .gif of the flash (from which the picture here, showing the flash as the dot of light in the center, is taken) at the story link and more info about the burst itself (and a larger animated .gif) at this link.

Oh, if you wonder about the name it was given, it's simple:
GRB = gamma ray burst
080319 = March 19, 2008
B = second (of four) gamma ray bursts detected that day

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