Solar System--sized Condensations in the Orion Nebula

The authors report high-resolution, VLA observations at 2 cm of 22 compact radio continuum sources toward the core of the Orion Nebula. This region contains the highest density of compact radio sources known. The sources are clustered mostly in the region of the Trapezium and the KL nebula. The brightest radio source on 1986 April 28 coincided with θ¹A Orionis. The diameters of the compact radio sources range from less than 4×10¹⁴cm (<27 AU) to ≡3.4×10¹⁵cm (≡230 AU). All six of the optically visible "nebular condensations" observed by Laques and Vidal (1978) have radio counterparts. Two models for these objects are presented: (1) dense, molecular globules (embedded in the diffuse H II region) with thin but dense ionized envelopes; and (2) low-mass stars (≡1 M_sun;) surrounded by an evaporating protostellar accretion disk. In both cases, ionization is external, produced by UV radiation from θ¹C and other Trapezium stars.