Question: How does Gas in space glow?

Sam Geen answered on 10 Nov 2020:

It glows for about the same reason that fire glows. Light is made or absorbed when electrons in atoms gain or lose energy. There are two ways that stars make this happen. One is that light from stars hits atoms in the gas in space, and the electrons get a bit more energy for some time before they release it again as light. Another is that atoms from the star move out at super high speeds (up to around a percent of the speed of light!) in a “stellar wind”, and when these atoms collide with the atoms in the gas around the star, this shocks it and also makes it glow. Sometimes the electrons get so much energy that they leave the atom and float around in space on their own in a “plasma”. By looking at pictures from telescopes, we can learn a lot about how stars work and how they shape the universe.