The Orion star formation complex. A better understanding for the origin of young clusters

The Orion complex is one of the best-studied regions in the sky. It is the closest massive star-forming region to earth, which harbors molecular clouds and various stellar groups at different evolutionary stages (up to 20 Myr) and with different masses. Therefore, it offers the closest laboratory to study the formation of clusters and stellar groups in different environments on the same large gas complex. Recently, we were able to analyze the 6D phase space of the southern Orion molecular cloud complex by using Gaia observed YSOs as probes for cloud distance and proper motion. This is a valid approach, since these YSOs still reside close to their parental cloud and they share, on average, the same radial velocity as the gas. The results show an expansion of the studied clouds on the 100-pc scale, implying a feedback-driven star formation history, likely from previous generations of massive stars that formed early in Orion. We call this feedback event the Orion big-blast event (Orion-BB), which took place about 6 Myr ago, based on a dynamical traceback. This event was able to form, or at least shape and compress, the molecular gas and likely triggered/enhanced star formation in the region. Additionally, young stellar clusters in the region (Ori, NGC1977) seem to be affected similarly. Our analysis shows that young stars remember the motion of their parental cloud. Our results imply that by observing young open clusters in the solar neighborhood, we could learn about the star-forming region in which they formed. For Orion-like regions, the resulting outcome (stellar clusters, associations, groups) will have characteristic space motions traceable for about several ten Myr before they eventually settle at different and unrecognizable orbits in the Milky Way.Funding: The Austrian Research Promotion Agency FFG (AT), Grant Number 873708, https://www.ffg.at/e