The Whirlpool galaxy (or
was first discovered by Charles Messier on October 13th
1773. Its companion NGC5195 was
discovered on March 21st 1781 by Messier's friend Pierre
Méchain. There does not seem to be an agreement on the
distance from Earth with values between 20 and 37 Million
light years, with the
Hubble site stating 31 Million light years.
Irish astronomer William Parsons (also
known as Lord Rosse) first gave this galaxy the name
inspired by its distinctive spiral shape.
Whirlpool galaxy is too far away
from us, the stars we see "in it" are actually in the Milky
Way and thus they are really in front.
According to our present understanding,
the pronounced spiral structure is a result of M51's current
encounter with its neighbour,
NGC5195 (the fainter one in
Messier's description). Due to this interaction, the gas in
the galaxy was disturbed and compressed in some regions,
resulting in the formation of new young stars. As is common
in galactic encounters, spiral structure is preferably
induced in the more massive galaxy.
This image was entered in
the April challenge at
astrophotogallery.com and finished second. Afterwards I
improved it slightly to what is displayed here. You can
compare with the old image by mouse over the image (the old
image then appears).