The M51 "Whirlpool Galaxy" shines as one of the brightest spiral galaxies in the night sky.
Several NASA space observatories combined to produce this composite image. The Chandra X-ray Observatory shows purple, point-like sources that indicate black holes and neutron stars in binary star systems, and also picks up on the glow of hot gas lighting the space between the stars. The Hubble Space Telescope provides optical data in green, while the Spitzer Space Telescope sees red infrared emissions — both reflect lanes of stars, gas, and dust in the galaxy's spiral arms. The Galaxy Evolution Explorer completes the image with views of hot, young stars giving off ultraviolet energy in blue.
The spiral shape may be a result of a galactic encounter when NGC 5195 passed through M51's main disk about 500 million years ago. That gravitational tug-of-war likely triggered a new round of starbirth, as gravitational forces condensed gas and jump-started the process of star formation.