M51

This is a picture of a galactic collision in action. The larger galaxy on the left is designated M51 or NGC 5194, while the smaller one on the right is called NGC 5195, and they lie about 37 million light years away. Most people think that the spiral arms of a galaxy are fixed features (stars that are in an arm, stay in an arm, arms stars that are between arms, stay between arms), and rotate around the center of the galaxy like a pin wheel. Actually, the arms of a galaxy are more like the waves in the ocean. One day you are sitting in between two spiral arms, and, 100 million years or so later, the stars have been pushed closer together, and you are now in the middle of an arm. 100 millions years later still, and the wave of the arm has passed you by, and you are in a trough again. When another galaxy gets close to you, the gravitational interactions cause the "galactic seas" to get really rough, and these "waves" get very strong. hat's why the arms in M51 are so pronounced.

Object	M51 -- Spiral Galaxy
Constellation	Canes Venatici
Date Aquired	05/15/2002
Camera	ST-7E with CFW-8
Exposure	10X5Min L, 3X5Min R (2X2) , 3X5Min G (2X2) , 3X8Min B (2X2)
Telescope	Meade Starfinder 10" @f/4.5
Mount	Losmandy G11