A New Look at the Molecular Gas in M42 and M43: Possible Evidence for Cloud–Cloud Collision that Triggered Formation of the OB Stars in the Orion Nebula Cluster
Yasuo Fukui et al 2018 ApJ 859 166
New molecular data from the Orion Nebula Cluster suggest that that the two clouds collided with each other < 0.1 Myr ago, triggeing the formation of the high-mass stars observed.