Spectacular in its clarity, this image of M51- the Whirlpool Galaxy in the constellation of Canes Venatici- was taken by the Hubble Space Telescope, high above the blurring effects of the earth’s atmosphere. It reveals the true nature of galactic spiral arms: immense structures of gas, dust, and clusters of stars curving through the emptiness of outer space. The size of this system boggles the mind. If one were to reduce our own solar system of planets- billions of miles in diameter itself- down to the size of a cookie, this galaxy in proper scale would be larger than the entire United States! Spiral galaxies rotate everything in them in immense orbits that take millions of years to complete.