By: Courtney Lee & Kristel Curameng

 Short-lived bursts of gamma-ray photons.  Gamma-ray photons are the most energetic form of light.  Some are associated with special types of supernovae.  Supertnovae are explosions marking the deaths of massive stars.

 Lasts anywhere from a few milliseconds to several minutes.  Shines hundreds of times brighter than a typical supernova.  Shines about a million trillion times as bright as the Sun.  Gamma-Ray Bursts are briefly the brightest source of cosmic gamma-ray photons in the observable universe.

 About once a day, the sky is lit up by a brilliant flash of energy.  It comes from random directions, different every time.  Brightest objects in the sky.  Human eyes cannot detect Gamma-ray bursts.

 The closest Gamma-ray burst known to date is over a hundred million light-years away.  Most of them come from billions of light years.  They outshine our closest stars in our sky from distances that are billions of times further away.  Stupendous amounts of energy are required.

 Discovered in the late 1960s by U.S. military satellites.  The satellites carried gamma-ray detectors since a nuclear explosion produces gamma rays.

 Gamma-ray bursts used to be the biggest mystery in high-energy astronomy.  In the early 1900s, astronomers didn’t know if they originated at the edge of our solar system, in our Milky Way Galaxy, or far away near the edge of the observable universe.  Today, satellite observations, follow-up ground-based observations, and theoretical work have allowed astronomers to link Gamma-Ray Bursts to supernovae in distant galaxies.

 Most Gamma-ray bursts come from other galaxies.  Often from among the most distant galaxies in the known universe.

 No one knows for sure  Our best theory is based upon several observed facts:  The only way to generate huge quantities is via gravitational collapse, and black holes can be very efficient at turning this energy into explosive power.  Some of the closest GRBs appear to occur simultaneously with supernovae  Almost all GRBs happen in galaxies containing large numbers of very massive stars.

 a duration of less than about two seconds  Are more rare, and astronomers were never able to detect an afterglow of a burst until recently.  The blast of energy only lasts for a few microseconds and then it’s gone.  shorter bursts have no detected afterglow in X-rays or visible light.  short GRBs may happen when two objects called neutron stars merge together, to form an even more bizarre object, a black hole. Or perhaps, some thought, a previously-formed black hole swallowed a neutron-star companion.

 have a duration of greater than two seconds  They are vast majority of explosions caused by a core-collapse supernova.  This is when a star many times larger than our own Sun runs out of fuel and then collapses inward to form a black hole. This also releases a massive outburst of energy that shines clear across the Universe.  Almost every well-studied long gamma-ray burst has been associated with a rapidly star-forming galaxy and in many cases a core-collapse supernova

 "Gamma-ray Bursts: Introduction to a Mystery." Imagine The Universe! Home Page. Web. 18 Apr  "Gamma-Ray Bursts." UC Berkeley Astronomy Department Home. Web. 18 Apr  "Gamma Ray Burst." Universe Today. Web. 18 Apr