This is an open cluster just 4 degrees south of Sirius, and in the
Canis Major constellation. Note the young bright blue white stars
as well as the highlight from some yellow giants. The brightest
being a 4.5 magnitude. This cluster is approx 2,300 light years
from earth and spans some 25 light years. Astronomers estimate it
at some 100 million years old.
It is said that Aristotle was the first to note this cluster in 325 BC,
then catalogued by Giovanni Batista Hodierna around 1654 and of course
by Messier in 1785.
Date: 10 Feb 12
Images 20-20sec stacked