Star Formation in the Orion Nebula I: Stellar Content

TL;DR

This paper reviews the extensive observations and understanding of the stellar content in the Orion Nebula, highlighting recent technological advances and their impact on knowledge of star formation, stellar populations, and cluster properties.

Contribution

It provides a comprehensive synthesis of multi-wavelength observations and recent technological developments in studying the Orion Nebula's stellar population and its implications for star formation.

Findings

Recent ultra-deep X-ray surveys reveal detailed stellar activity.

High-resolution monitoring improves understanding of binary systems.

Distance to the Orion Nebula Cluster is now constrained near 400 parsecs.

Abstract

The Orion Nebula is one of the most frequently observed nearby (<1 kiloparsec) star forming regions and, consequently, the subject of a large bibliography of observations and interpretation. The summary in this chapter is bounded spatially by the blister HII region, with sources beyond the central nebula that are part of the same dynamical clustering covered in other chapters in this book. Herein are discussed panchromatic observations of the massive OB stars, the general T Tauri population, the sub-stellar sources and variable stars within the Orion Nebula. First, a brief history of 400 years of observation of the Nebula is presented. As this history is marked clearly by revelations provided in each age of new technology, recent ultra-deep X-ray surveys and high resolution multi-epoch monitoring of massive binary systems and radio stars receive special attention in this review. Topics discussed include the kinematics, multiplicity, mass distribution, rotation, and circumstellar characteristics of the pre-main sequence population. Also treated in depth are historical and current constraints on the distance to the Orion Nebula Cluster; a long standing 10-20% uncertainty has only recently begun to converge on a value near ~400 parsecs. Complementing the current review of the stellar population is a companion chapter reviewing the molecular cloud, ionized HII region and the youngest protostellar sources.