78 Mind-Blowing Nebula Pics That Prove Just How Captivating Interstellar Space Is

Well, the specific term is "false colored." The way the human eyes see most of these objects, they tend to lack a lot of color. In these nebulae, the gasses are incredibly warm, and the atoms and molecules vibrate more, and release energy at special wavelengths. These special wavelengths can be taken in with special "narrowband filters". The narrowband filters only let in a narrow band of light, which can be used to learn all sorts of things about the nebula. Usually, astrophotographers do multiple hours of exposure through different wavelengths. The separate exposures can be stacked and modified individually, assigned with a certain color in the image processor. This is not the case of all astroimaging. Some do use real color as collected through the astrograph (read: fancy astronomy telescope-camera combination), but may be edited to increase certain aspects of the image. So yes, your friend is mostly correct. But no, it is not a 'paint by number' It is just combing different exposures, which are given a special color value, which is stacked onto the other exposures. (there is a ton of stuff to astrophotography, and I might be missing a few key points, but I hope i answered your question.)