M100: A Grand Design Spiral Galaxy
			
		
		
		
			Majestic on a truly cosmic scale, M100 is appropriately known as a 
grand design spiral galaxy. 
It is a large galaxy of over 100 billion stars with well-defined spiral arms that is similar to our own 
Milky Way Galaxy. 
One of the brightest members of the 
Virgo Cluster of galaxies, 
M100 
(alias NGC 4321) is 56 million light-years distant toward the constellation of 
Berenice's Hair 
(Coma Berenices). 
This Hubble 
Space Telescope 
image of 
M100 was made in 2009 and reveals bright blue 
star clusters and 
intricate winding 
dust lanes which are hallmarks of this class of galaxies. 
Studies of variable stars in 
M100 
have played an important role in determining the 
size and age of the Universe.
If you know exactly 
where to look, 
you can find a small spot that is a light echo 
from a bright supernova that was 
recorded a few years before the image was taken.