Of all the countless island universes scattered across the sky, none seem as
exciting as Messier Object 51 (M51), the renowned Whirlpool Galaxy. Once believed to be
a great swirling nebula, M51 is now known to be the finest example of a face-on spiral galaxy.
22 million light years distant, this picturesque pinwheel of stars, dust, and
gas measures about 65,000 light years across and shines with the luminosity of
10 billion suns.

The Whirlpool is just a few degrees southwest of the end star in the Big Dipper.
From dark, clear sites, high-quality 6- to 8-inch telescopes will readily show
M51's graceful arms arcing around its bright central core. Larger instruments
will bring out the galaxy's dark lanes and bright H II regions that dot its spiral arms.

Don't overlook M51's companion, NGC 5195, which apparently Messier did when he
observed M51 in 1773. Conspicuous in the small telescope, this satellite system
gives the appearance of being attached to the north spiral arm of M51.
This bridge between the two galaxies is actually an optical illusion - a spiral
arm of M51 is superimposed on NGC 5195 with NGC 5195 actually lying on the far
side of M51 (by perhaps 1/2 million light years), although the two galaxies have
had one or more close encounters in the past.

Gravitational interaction with NGC 5195 is thought to be triggering enhanced star
formation in M51, at a rate of about five new stars each year. This is similar to
the number forming per year in the Milky Way, but note that our galaxy has a mass
about 10 times that of M51.