The Orion Nebula is the closest region of massive star formation to Earth. Astronomers have observed protoplanetary disks, brown dwarfs, and the photo-ionizing effects of massive nearby stars in the nebula. The nebual has odd supersonic “bullets” of gas each ten times the diameter of Pluto’s orbit and tipped with iron atoms glowing bright blue piercing the dense hydrogen clouds believed to have been formed one thousand years ago from an unknown violent event.
Observers have long noted a greenish tint to the nebula, in addition to regions of red and areas of blue-violet. The green hue is caused by a low-probability electron transition in doubly ionized oxygen, a “forbidden transition” -radiation that is impossible to reproduce in the laboratory because it depended on the nearly collision-free environment found in deep space. The blue-violet coloration is the reflected radiation from the massive O-class stars at the core of the nebula.