The Whirlpool Galaxy (M51a or NGC 5194)
is a spiral galaxy about
24 million light-years' distant that is oriented
moderately close to perpendicular to the line of sight,
i.e., so the spiral is fully in view.
It is one of two galaxies that made up
M51 in the Messier Catalog, thus its
designation M51a.
It is classified as a grand design spiral galaxy,
i.e., showing a very clear spiral structure,
and also possesses an active galactic nucleus (AGN).
Its orientation makes it ideal for many
observations aimed at discovering the
architecture of spiral galaxies, such
as the frequency, location, and density
of molecular clouds.