This article is about a/an galaxy in Mighty Morphin Power Rangers.
Master vile comic

The M51 Galaxy is an expanse of space that is under the absolute rule of Master Vile, who resides on the planet Gamma Vile. With Friends Like These In his own words, it's "where evil reigns supreme and the bad guys ALWAYS win". Alien Rangers of Aquitar

Thousands of years ago, the people of the M51 Galaxy fled to Earth's moon and hid the Zeo Crystal deep inside the Caves of Deception so that Master Vile could not abuse its power. In addition to the various illusions in the caves, they placed a powerful force-field around the Crystal that would destroy anybody who was not pure of heart.

M51 in reality

M51, aka the 'Whirlpool galaxy', is a spiral galaxy between 15 and 35 million light years from the Milky Way. It is also known as Typhon Canum Venaticorum, named after Typhon, an evil god from Greek mythology.