The yellow nebula around Antares is a yellow reflection nebula. That is quite unusual. But the blue stuff around Rho Opiuchi (and star 22 Scorpii) is the good ol' normal blue reflection nebulosity! (And the pink glow near hot blue star Sigma Scorpii is the 656 nm emission from ionized hydrogen! Obviously!)
<<A glow discharge is a plasma formed by the passage of electric current through a gas. The simplest type of glow discharge is a direct-current glow discharge. In its simplest form, it consists of two electrodes in a cell held at low pressure (0.1–10 torr). A low pressure is used to increase the mean free path; for a fixed electric field, a longer mean free path allows a charged particle to gain more energy before colliding with another particle. The cell is typically filled with neon, but other gases can also be used. An electric potential of several hundred volts is applied between the two electrodes. A small fraction of the population of atoms within the cell is initially ionized through random processes, such as thermal collisions between atoms or by gamma rays. The positive ions are driven towards the cathode by the electric potential, and the electrons are driven towards the anode by the same potential. The initial population of ions and electrons collides with other atoms, exciting or ionizing them. As long as the potential is maintained, a population of ions and electrons remains.>>
Dark Dust and Colorful Clouds near Antares
