The Orion Nebula is one of the most scrutinized and photographed objects in the night sky, and is among the most intensely studied celestial features. The nebula has revealed much about the process of how stars and planetary systems are formed from collapsing clouds of gas and dust. Astronomers have directly observed protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars in the nebula. There are also supersonic "bullets" of gas piercing the dense hydrogen clouds of the Orion Nebula. Each bullet is ten times the diameter of Pluto’s orbit and tipped with iron atoms glowing bright blue. They were probably formed one thousand years ago from an unknown violent event. Observers have long noted a distinctive greenish tint to the nebula, in addition to regions of red and areas of blue-violet. The red hue is well-understood to be caused by Hα recombination line radiation at a wavelength of 656.3 nm. The blue-violet coloration is the reflected radiation from the massive O-class stars at the core of the nebula.
Image Credit: NASA/JPL-Caltech/ Wikipedia