Imaging the Ionized Disk of the High‐Mass Protostar Orion I

We have imaged the enigmatic radio source I (Orion I) in the Orion KL nebula with the VLA at 43 GHz with 34 mas angular resolution. The continuum emission is highly elongated and is consistent with that expected from a nearly edge-on disk. The high brightness and lack of strong molecular lines from Orion I can be used to argue against emission from dust. Collisional ionization and H - free-free opacity, as in Mira variables, require a central star with ≳10 5 L ☉ , which is greater than infrared observations allow. However, if significant local heating associated with accretion occurs, lower total luminosities are possible. Alternatively, photoionization from an early B-type star and p + / e - bremsstrahlung can explain our observations, and Orion I may be an example of ionized accretion disk surrounding a forming massive star. Such accretion disks may not be able to form planets efficiently.