This false color image of the Whirlpool Galaxy is a combination of images taken at three different wavelengths: visible light is ren- dered as red, radio emission is green, and H I gas is blue. The striking spiral arms show up distinctly in all colors. The brightest ridges of radio emission lie mostly along the dark dust lanes, which are seen in visible light. Because radio emission comes from the hot gas surrounding new stars and visible light comes from the stars themselves, astronomers have deduced that the regions of current star formation are buried within clouds of dust.
It is interesting to note that the H I gas, although it follows the spiral arms, is not concentrated where the stars are located. This hydrogen gas,
