Blue Stragglers in Globular Clusters
			
		
		
		
			This old dog is doing new tricks.  On the left is ancient 
globular cluster 
47 Tucanae 
which formed many billions of years ago.  
On the right is a closeup of its dense stellar center by the 
Hubble Space Telescope, 
released last week.  
Circled are mysterious stars called 
"blue stragglers."  Stars as bright and blue as blue stragglers 
live short lives, much shorter than the age of the host 
globular cluster itself.  
But this contradicts evidence that 
globular cluster 
stars formed all at once.  
Although this problem has been known for almost 50 years, 
a mass and spin rate for a blue straggler was first published last Saturday.  
This new information indicates that BSS 19 was rejuvenated by 
two orbiting stars slowly coalescing , 
and not by a dramatic collision.