H-alpha Image of M82
This image shows an H-alpha image of M82. The temperature of H-alpha emitting gas is (probably) around 10000 K and may be heated by shocks and hot stars. The large extent (around 6 kpc) of the emission results from a superwind blowing out of the galaxy. The high supernovae rate in M82 (around one every ten years) is thought to be the power source driving out the superwind. The scale of the image is 10' by 10', or 10 kpc by 10 kpc assuming a distance to M82 of 3.6 Mpc.