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Credit & Copyright: Thomas V. Davis    
(tvdavisastropix.com)  
  
  
Explanation:
In 1714,  
Edmond Halley  
noted that M13 "shows itself to the  
naked eye when the sky is serene and the Moon absent."  
  
Of course, M13  
is now modestly recognized as  
the Great Globular Cluster in Hercules,  
one of the brightest  
globular  
star clusters in the northern sky.  
  
Telescopic views reveal the  
spectacular cluster's hundreds of thousands  
of stars.  
  
At a distance of 25,000 light-years, the cluster stars  
crowd  
into a region 150 light-years in diameter,  
but  
approaching the cluster core  
upwards of 100 stars could be contained  
in a cube just 3 light-years on a side.  
  
For comparison, the  
closest star to the Sun is over  
4 light-years away.  
  
Along with the cluster's dense core, the outer reaches of M13  
are highlighted in  
this  
deep color image.  
  
A distant background galaxy,  
NGC 6207  
is also visible above and  
to the right of the Great Globular Cluster  
M13.  
  
 
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Based on Astronomy Picture
Of the Day
Publications with keywords: globular cluster - M 13
Publications with words: globular cluster - M 13
See also:
