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Biggest Ever Cosmic Explosion Observed 7.5 Billion Light Years Away

by Ian O'Neill on March 20, 2008

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The 19th March gamma ray burst (credit: NASA)
A record-breaking gamma ray burst was observed yesterday (March 19th) by NASA’s Swift satellite. After red-shift observations were analysed, astronomers realized they were looking at an explosion half-way across the Universe, some 7.5 billion light years away. This means that the burst occurred 7.5 billion years ago, when the Universe was only half the age it is now. This shatters the record for the most distant object that can be seen with the naked eye…

Gamma ray bursts (GRBs) are the most powerful explosions observed in the Universe, and the most powerful explosions to occur since the Big Bang. A GRB is generated during the collapse of a massive star into a black hole or neutron star. The physics behind a GRB is highly complex, but the most accepted model is that as a massive star collapses to form a black hole, the in falling material is energetically converted into a blast of high energy radiation. It is thought the burst is highly collimated from the poles of the collapsing star. Any local matter downstream of the burst will be vaporized. This has led to the thought that historic terrestrial extinctions over the last hundreds of millions of years could be down to the Earth being irradiated by gamma radiation from such a blast within the Milky Way. But for now, all GRBs are observed outside our galaxy, out of harms way.

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An artists impression of gamma ray burst (credit: Stanford.edu)

This record-breaking GRB was observed by the Swift observatory (launched into Earth orbit in 2004) which surveys the sky for GRBs. Using its Burst Alert Telescope (BAT), the initiation of an event can be relayed to Earth within 20 seconds. Once located, the spacecraft turns all its instruments toward the burst to measure the spectrum of light emitted from the afterglow. This observatory is being used to understand how GRBs are initiated and how the hot gas and dust surrounding the event evolves.

“This burst was a whopper; it blows away every gamma ray burst we’ve seen so far.” – Neil Gehrels, Swift principal investigator, NASA Goddard Space Flight Center, Greenbelt, Md.

This particular GRB was observed in the constellation of Boötes at 2:12 a.m. (EDT), March 19th. Telescopes on the ground and in space quickly turned to Boötes to analyse the afterglow of the burst. Later in the day, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst’s redshift at 0.94. From this measure, scientists were able to pinpoint our distance from the explosion. This red shift corresponds to a distance of 7.5 billion light years, signifying that this huge GRB happened 7.5 billion years ago, over half the distance across the observable universe.

Source: NASA

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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

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  • Pedro

    Visible to the human eye? How can we try to find it? Constellation? Hemysphere? Well… if it is south one… game over to me! But if it’s north i would like to see it very much! Can someone help me?

  • Mark

    I witnesssed this with the naked eye. My daughter and I were star gazing and I happened to be extremely lucky to be looking right at it when it occurred. I was in my driveway in Dayton, OH area.

    Didn’t realize what I was witnessing until reading about it later on the net.

  • Michael

    Traveling 7.5 billion light years, like any light or cosmic rays, the dispersal is immense – at that distance, the gamma rays are harmless. And it will no longer be visible with the unaided eye because GRB’s are relatively brief events – the afterglow barely visible with a highly specialized telescope.
    But ponder this: with science claiming an age for the universe at about 13.7 billion years – how is it the universe supposed to be over 150 billion light years across?
    And with the moon about 240.000 miles distant, why did it take days, for the Apollos to reach at 25,000 mph, (instead of about 10 hours)?

  • Michael

    Not being particularly religious by nature, I still ponder the beginnings of it all and the structure of matter and energy – the relationship between light, gravity and electromagnetiism – the strong and weak nuclear forces. The possibility that a grand unification theory is real – and was laid down by an omnipotent designer/mathematician.
    Oops… maybe I am religiuos, but when the religiuos begin to group, I get nervous.

  • Michael

    *religious even

  • holyavengerone

    Michael said: “And with the moon about 240.000 miles distant, why did it take days, for the Apollos to reach at 25,000 mph, (instead of about 10 hours)?”

    For that one, I can tell you one thing: they didn’t go there in a straight line. They did increasingly larger orbits until they reached it. So they did travel a lot more than the 240,000 miles you quote.

    As for the size of the universe, not sure where you get your number from, but it can be explained by space inflation, especially in the first few moments of the universe.

  • alphonso richardson

    Wow, Mark, you & your daughter were very lucky – you get to talk about a possible once-in-a lifetime event.
    I is well jealous

  • Mark

    Thanks Alphons. Yes, we were ridiculously lucky. I have checked several blogs to see if any one else has reported seeing thi sevent and so far – noone.

    Could it be possible we were the only ones on the planet to see this? Any one else out there know of any one that has seen this?

  • Michael

    holyavengerone
    Increasingly larger orbits? Orbiting what? Sorry, but that makes no sense, whatsoever.
    The Apollo settled into earth orbits before increasing speed to break free and begin the journey to moon orbit, (a distance of about 240,000, possibly as much as 255,000 miles because of the moon’s eliptical orbit). So why would it take days, ( I keep hearing 3 or so), at 25,000 mph?
    And the trajectories were very near a straight line.

  • Michael

    And a universal, iron-clad law of physics, proposed by Einstein and endosed by the physics community, is that nothing, ever, can travel faster than the speed of light. Hence my curiosity about a universe supposedly more than 150 bliion light years across having been formed in about 13.7 billion yerars. Maybe some cosmic math that completely escapes me.

  • Maccas

    Michael said: “And with the moon about 240.000 miles distant, why did it take days, for the Apollos to reach at 25,000 mph, (instead of about 10 hours)?”
    …..Clearly the additional time was to provide for the need for long Ad breaks on TV due to the worldwide commercial interest in going to the moon ;)

    re your question of the size of the Universe. I don’t know where the 150B comes from but I put a related question to an online uni astronomer and was told something like (hope I got this right as was years ago now) – that the universe didn’t start as a single point 13.7 billion years ago that exploded out from such that there is a “centre” but more of a soup that changed at the point of the big bang and expanded from that to present day. what we see as the universe continues to expand is that around us that light left 13.7B years ago, ie. it is much larger than what we see we just see the sphere around us of light just reaching us now that started 13.7B years ago. hmmm..the more I think about this the more I get screwed up…help!?

  • Maccas

    Mark,
    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, maybe nearly as bright as Venus 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 & it didn’t look as though it wasn’t going to fade but then faded.
    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 backyard 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. I think I could reconstruct more detail as the event stuck in my mind thats for sure & I made a reasonable 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 but I think I started to go to the phone when it faded.

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