NASA’s Space Telescope Swift detected a powerful Gamma Ray Burst on March 19th in the Constellation Bootes called GRB080319B. Apparently, the blast was visible to the naked eye during 20 to 40 seconds, though no one actually remarked it because gamma rays are blocked by the atmoshpere, but also because it was just on the limit of naked-eye visibility. But the Swift telescope was built especially to track Gamma Ray Bursts, simply because these events last for a short amount of time. I suggest that you track the daily bursts detected by Swift on this page, where a little paragraph describes each burst.

The reasons to why Gamma Ray Bursts are still ambiguous today. Researches speculate that gamma ray bursts happen when large stars run out of fuel, that is Hydrogen gas. Their nuclei collapse and form black holes, neutron stars, and pulsars. When this happens, a huge amount of energy is released in the form of Gamma Rays, which are in practice the most energetic form of light. They then cross the universe at the speed of light, and heat gas clouds creating powerful glowing phenomena.
NASA states that “Gamma ray bursts are the most luminous explosions in the universe since the big bang.”

Watch the Video of the Gamma Ray Burst just below, monitored all night by the “Pi of the Sky” Camera

Powerful Gamma Ray Bursts can also occur when a Neutron Star falls into a Black Hole, like in This Video (or Read the Explanation). This is the possible explanation for the extremely powerful Gamma Ray Burst that occured in 1998.

It has been reported that the distance of the burst is of 7.5 billion light-years. This means that the burst actually occured 7.5 billion light years ago because the distance separating Earth from this distant star is so large that it has taken 7.5 billion years for the light to reach our eyes.

Read more about this at NASA and at Slacker Astronomy.