The Whirlpool Galaxy is a classic spiral galaxy.
At only 15 million light years distant, M51,
also cataloged as NGC 5194,
is one of the brighter and more picturesque galaxies
on the sky. The smaller galaxy appearing here above and to the
right is also well behind M51,
as can be inferred by the dust in M51's
spiral arm blocking light from this smaller galaxy. Astronomers
speculate that M51's spiral structure
is primarily due to it's gravitational interaction with this smaller
galaxy.
On This Day in Space History
On January 25, 2004, NASA's Opportunity rover landed in Meridiani Planum on Mars.
