Short Gamma-Ray Bursts Localized
			
		
		
			Illustration Credit :  Dana Berry, 
NASA
		
		
			What causes gamma-ray bursts?  
The most energetic type of explosions known in the cosmos has been an enigma since 
discovered over 30 years ago.  
It now appears that there may not be one unique type of progenitor.  
Long duration 
gamma-ray bursts (GRBs) have been 
localized, over the past few years, to 
blue regions in the universe rich in star formation.  
Massive young stars nearing the end of their short lives commonly explode in these regions.  
Astronomers associate these 
long duration GRBs, that can last from seconds to minutes, 
with a type of stellar explosion common in young massive stars.  
Over the past few months, short duration GRBs have finally been 
localized and found to occur in different types of regions -- not only 
blue regions rich in star formation.  
Many astronomers therefore now theorize that 
short GRBs, which typically last less than one second, are the result of a 
different progenitor process 
than long GRBs.  
A leading model is that a short GRB will occur when a 
neutron star 
either impacts 
another neutron star or a 
black hole.   
Such collisions may occur well after star-forming regions have otherwise burned out.
Pictured in the  above illustration, two energized 
neutrons stars finally approach 
each other in their orbits, a death spiral that might end with a short GRB.