Blinding Gamma Ray Burst Was Directed at Earth
Written by Nancy Atkinson
Artists depiction of GRB 080319B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones
On March 19, 2008 at 2:13 am EDT, NASA's Swift satellite detected an explosion from the constellation Bootes, and sent an alert to ground-based telescopes. At the same moment, the Russian KONUS instrument on NASA's Wind satellite and a robotic wide-field optical camera called "Pi of the Sky" in Chile captured the first visible light from this incredibly bright and powerful gamma ray burst. Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. For a few moments, the GRB had a million times the luminosity of the entire Milky Way Galaxy. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away. Astronomers say the reason this gamma ray burst was so bright was that it was aimed almost directly at Earth.
Observations of the event, formally named GRB 080319B, are giving astronomers the most detailed portrait of a GRB ever recorded. "You have to have the satellites in orbit and the rapid response telescopes on Earth in order take complete advantage this rare kind of event," said David Burrows, head of the Swift X-ray telescope team, at today's press conference detailing the GRB.
Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst's extraordinary brightness arose from an unusual two component jet that shot material directly toward Earth at 99.99995 percent the speed of light.
Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away.
Immediately after the blast, Swift's UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event. A head-on burst directed towards Earth only occurs by chance only about once a decade, so GRB 080319B is a rare catch.
Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star's core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.
The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider. "A normal signature is different from what we saw in this burst," said Racusin . "In this object, we see two signatures of jets with two different properties."
"Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time," says team member Stefano Covino. "We happened to view this monster down the barrel of the very narrow and energetic jet."
These unique beacons of light were observed only 8 minutes after the trigger, and are the brightest bursts ever detected. Additional study of this event can also help provide more information on relativity and cosmology.
Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. "It's been postulated that a nearby gamma ray burst directed at earth could affect our atmosphere, causing something like a nuclear winter. We are fortunate in that we don't believe there are any stars in our galas that will produce a gamma ray burst."
NASA, NASA News Audio
Filed under: Gamma Ray Bursts
September 15th, 2008 at 10:00 am
The article was correct:
http://apod.nasa.gov/apod/ap080328.html
" The source of that burst has been discovered to lie over halfway across the Universe at a distance of about 7.5 billion light-years. Now holding the distinction of the most distant object that could be seen by the unaided eye and the intrinsically brightest object ever detected"
September 15th, 2008 at 10:22 am
@Xenophon: The nearest galaxy is more like 2 million light years away. As for Hubble, it wasn't looking in the Milky Way as Burrows said (apologies for the entire quote): 'Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. "It's been postulated that a nearby gamma ray burst directed at earth, could affect our atmosphere, causing something like a nuclear winter. We are fortunate in that we don't believe there are any stars in our galas that will produce a gamma ray burst." '
Moreover, if the Hubble's limit is 13 billion light years, then 7.5 billion is within reach for the Hubble to detect. What is it that doesn't add up? Perhaps… the wording in the article?
'
September 15th, 2008 at 12:10 pm
A GRB traveled 7.5 billion light-years in a direction that
allowed wonderful observations from Earth and satellites.
How could that have been "aimed" or "directed" toward an
Earth that would not exist for another ~3 billion years?
From the article:
Covino: "… down the barrel of the … jet."
Burrows: "… postulated that a nearby GRB directed at earth …"
NA: … aimed almost directly at Earth.
NA: … shot material directly toward Earth …
NA: A head-on burst directed towards Earth …
NA: The team believes the jet directed toward Earth …
Perhaps a future version of this writeup could use
constructions that does not imply intent or foreknowledge,
such as "in the direction of" or "jet that travelled toward
Earth's current location", rather than risking readers taking
"aimed" and "directed towards" as clear evidence of the
FSM's far-reaching and all-knowing powers and capabilities.
September 15th, 2008 at 1:20 pm
help out here seem to be a little lost with the usage of the present tense you made seem like the burst just occured inspite of that great distance of 7.5 billion light years away i would presume that burst occured alittle 7.5 billion years ago more in respect to the seep of the gamma rays 99.9999…… am right ?
September 15th, 2008 at 10:12 pm
The road of assumption is lined with coffins.
September 15th, 2008 at 11:19 pm
your diagram is too small. the wording cannot be made out even if we click the diagram and see if it expands.
September 17th, 2008 at 5:36 am
I had a GRB once after eating at Taco Bell
September 18th, 2008 at 11:58 am
"Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. "It's been postulated that a nearby gamma ray burst directed at earth could affect our atmosphere, causing something like a nuclear winter.""
So THAT'S what killed the dinosaurs! I always thought the "big rock falling from the sky" theory was a bit silly….
September 28th, 2008 at 7:01 am
@ GRaBoid -
You got the impression that the article was saying this was purposely 'aimed' ? That strikes me as odd !
And yes, if it's 7.5 billion light years away, that means it happened 7.5 billion years ago. The Sun wasn't even a twinkle in the eye of cold interstellar gas.
October 12th, 2008 at 11:02 pm
Just some brief comments:
It may have been aimed in that direction, where Earth is now; however, neither our planet existed then- event ocurred before it's creation-, nor was our planet- then- where it is now, thus it is not feasible for GRB to have been "aimed" at our planet. One can be just a tad more realistic and see that the GRB ocurred as part of it's process, and by shear "luck, we have been in the path of one of it's lines of travel, we can be realistic, hopeful, and with our feet solidly on the ground, and then we can evaluate things with more coherence, which allows us to see with more clarity any and all events that happen out there. Thank you. Javier
October 12th, 2008 at 11:27 pm
re Leigh, September 10th, 2008 at 6:42 pm
"im sure iv seen one once i was looking up at the stars in my garden and one came and went in 5 seconds it was very bright and then just nothing strange i still wonder what it was i saw that night the sky was very clear and full of stars thanks~"
Back about Sept 2000 in the southerly direction of the Southern Cross (am in Australia) I saw a similar event in the sky to that you describe but which lasted for about 20sec before fading & was very bright similar to other stars around it if not brighter if I recall correctly (long ago now). It illuminated to maximum brightness quickly, caught my attention, was steady in brightness & without motion & I remember thinking it couldn't possibly be a meteor & looked as though it was there to stay but then faded away.
I assumed it may have been a supernova at the time but didn't know what to do about it or who to call etc. & assumed somebody more important than a casual observer would have spotted it. I would like to know more about what it may have been if anybody knows of such an event around that time & location. I think I could reconstruct more detail as the event stuck in my mind thats for sure & made a good mental note of it, time, date, approximate location in the sky. Trouble is I thought that if it was something very far away then even a small amount area of sky is still a huge area. Regret not following up at the time now.
Re comments about "aimed" etc. - Guys don't get your knickers in a knot
- I think we all know it wasn't actually "aimed" how stupid do you think we are…..& if you actually are that stupid to believe it was "aimed" well may the force be with you and keep you safe, warp 10 Scotty! 
Cheers.
November 13th, 2008 at 12:59 am
It's amazing to realize how little we understand. For example the velocity of our sun relative to the black hole at the center of our galaxy. There are too many vectors to be taken into consideration. Even for an entire planet of astrophysicists.
December 15th, 2008 at 8:26 am
It's amazing to me that most comments are splitting hairs over the common usage of the word "AIMED" ….