Spiral Galaxy M74

About This Photograph

M74 is often cited as a prototypical "grand design" spiral galaxy. Winding out from the central core of older yellow suns, its graceful arms trace the wave of formation of new stars in the disk of the galaxy. The magenta patches are clouds of energized gas where new stars are just being born, similar to our own galaxy's Orion Nebula. Once they dissipate, these clouds leave behind bluish clusters of hot, young stars, also visible in this photograph.

Apparently spiral arms such as these are transient phenomena, and do not rotate along with the rest of the material in the galaxy's disk. Rather, they are compression waves traveling through the disk, triggering star formation as they propagate.