What Causes Gamma Ray Bursts ?

   

     Imagine a single blast of energy powerful enough to destroy the equivalent of a thousand Earths in a second. Explosions of that magnitude happen in the universe every day, thanks to gamma ray bursts. Scientists didn’t know these extreme bursts of energy existed until the 1960s, when satellites designed to monitor nuclear weapons tests on Earth picked up the phenomenon. A long the electromagnetic spectrum of energy—which includes radio waves, ultraviolet waves, and visible light— gamma rays are the most powerful. A gamma ray burst is a focused stream of energy that can last from just a few seconds to several minutes. Just one 10- second burst releases more energy than our Sun will produce over its 10-billion-year lifetime. Most bursts occur outside theMilky Way in galaxies with many massive stars.

    Today scientists have two main theories to explain what might cause a gamma ray burst. One idea involves neutron stars. If two of these massively dense stars orbit each other and their orbits start to decay because of gravitational pull, they collide. That collision creates a black hole. Before some of the stars’ matter tumbles into the black hole, it releases energy that some scientists think produces a gamma ray burst.

    The second theory gives hypernovas credit for the bursts. The “death” of a star with a mass 10 times greater than the Sun’s creates an explosion called a supernova. The death of an even more massive star creates a hypernova explosion. Hypernovas might cause some gamma ray bursts. Scientists also consider that both theories might be accurate: Neutron star collisions create short bursts, and hypernovas create longer ones. Or another process the scientists haven’t considered could explain all the bursts.

    Knowing what causes gamma ray bursts may not be as important as understanding how they could affect Earth. In 2014, astronomers Tsvi Piran and Raul Jimenez calculated fairly high odds that a past gamma ray burst caused a mass extinction of life on Earth. Long-ago bursts might also explain why humans have not yet found life on other planets .