This striking image traces the H I gas in the Whirlpool Galaxy. The spiral arms can be seen here, but there is no trace of either WhirpoolΓÇÖs nucleus or that of its companion galaxy NGC 5195.
The colors here indicate that the gas clouds in Whirlpool are orbiting the galaxyΓÇÖs nucleus. The blue gas is approaching us, the red gas is moving away. By analyzing this rotation, astronomers can determine the mass of the galaxy and can even deduce the presence of matter not visible at any wavelength of light.
