Spiral galaxy NGC 7331. Spitzer Space Telescope infrared image of the spiral galaxy NGC 7331. This galaxy lies around 50 million light years from Earth in the constellation Pegasus. Notable in this image is the bright yellow ring of star formation around the galaxy's centre. The ring has a radius of 20,000 light years and is made up of polycyclic aromatic hydrocarbons (PAHs), with enough material to form about four billion stars of the magnitude of our Sun. The three galaxies below NGC 7331 are about 10 times farther away. Wavelengths of 3.6 microns are coloured blue, 4.5 microns are green, 5.8 microns are yellow and 8.0 micron wavelengths are red.