This map shows the position of almost every known gamma-ray burst (often called GRBs), at least those for which astronomers have been able to measure a position (GRBs are often detected without any way of knowing where exactly they came from). The map is an equirectangular projection of the night sky in galactic coordinates, showing the entire sky as visible from Earth with our Milky Way galaxy running through the middle. The size of each circle illustrates the relative brightness (as seen from Earth) for each GRB, and the length of time each circle persists is scaled to 1/20th of the true length of the burst. Note that many of the earlier GRBs were detected by instruments that were not able to measure the true brightness or length of the burst - average values are used when showing these bursts on the map. The slider on top of the page lets you move through history, exploring when different GRBs were first discovered. Look to the counter in the top right to see what date range is currently shown, and click on any GRB to learn more about it.
A gamma-ray burst is a short flash of incredibly high-energy light (gamma-rays). There are two major types, called long and short GRBs because of the length of time of the burst. Long GRBs are more common and usually last about 30 seconds, while short GRBs last only an average of 0.3 seconds. Long gamma bursts seem to be associated with core-collapse supernovae of incredibly massive stars, also known as hypernovae. In a hypernova, the core of the star collapses into a black hole and relativistically-beamed jets of gamma-rays blast out of the exploding star, forming the short and bright bursts we see here on Earth. Short GRBs are less well-understood, but many researchers believe they could be caused by the merger of two neutron stars - exactly what causes short GRBs is an important question that researchers are still working to figure out.
Our atmosphere does not allow gamma-rays through it, which is usually a good thing because it protects us from their damaging effects. However, it does make it difficult to study GRBs. In fact, the main tools researchers use to detect GRBs are space satellites, flying far above the Earth's atmosphere. The first GRB was detected in 1967 by the Vela satellites which were built by the USA to detect nuclear weapons testing by the Soviet Union (nuclear bombs emit gamma-rays). The military knew that the bursts they detected were not caused by nuclear testing but did not know what could be causing them. The early detections were classified until 1973, when the USA made the first public announcement describing these inexplicable bursts. There have now been several generations of satellites designed to help study GRBs and we've learned a lot more about them (see here for a good summary). The map on this page includes all of the GRBs astronomers have been able to observe with well-measured positions - right now, that's GRBs.
Because they come from very distant galaxies (which are equally spaced in all directions), GRBs happen all over the sky. Most of the trends and patterns visible in the animation above are due to the methods astronomers use to look for and discover GRBs and are not real trends in GRB properties. For example, early GRB-detecting satellites were not very good at measuring how long a GRB lasts, and so the early GRBs are shown with an average duration, while the more recent GRBs are shown to fade over a length of time scaled to their true (observed) duration. Here are a few other interesting trends:
This website was built by Isaac Shivvers, an astrophysics graduate student at UC Berkeley. Feel free to contact me with any questions or comments at ude.yelekreb.ortsa@srevvihsi.
The GRB data behind this site was assembled from NASA's Gamma-Ray Burst Catalog, the SWIFT Gamma-Ray Burst Table, and the FERMI Gamma-Ray Burst Catalog. The map is automatically updated with newly-discovered GRBs every week.
The background image of the night sky is courtesy of ESO/S.Brunier, and was produced as part of the European Southern Observatory's GigaGalaxy Zoom project.
© Isaac Shivvers, 2013
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