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Orion Source I (`SrcI') is the protostar at the center of the Kleinmann-LowNebula. ALMA observations of SrcI with 0.2" angular resolution were made at 350and 660 GHz to search for the H26alpha and H21alpha hydrogen recombinationlines and to measure the continuum flux densities. The recombination lines werenot detected, ruling out the possibility that SrcI is a hypercompact HIIregion. The deconvolved size of the continuum source is approximately 0.23 x0.07" (100 x 30 AU); it is interpreted as a disk viewed almost edge-on.Optically thick thermal emission from ~500 K dust is the most plausible sourceof the continuum, even at frequencies as low as 43 GHz; the disk mass is mostlikely in the range 0.02 to 0.2 Mo. A rich spectrum of molecular lines isdetected, mostly from sulfur- and silicon-rich molecules like SO, SO2, and SiS,but also including vibrationally excited CO and several unidentifiedtransitions. Lines with upper energy levels E_U > 500 K appear in emission andare symmetric about the source's LSR velocity of 5 km/sec, while lines with E_U< 500 K appear as blueshifted absorption features against the continuum,indicating that they originate in outflowing gas. The emission lines exhibit avelocity gradient along the major axis of the disk that is consistent withrotation around a 5-7 Mo central object. The relatively low mass of SrcI andthe existence of a 100 AU disk around it are difficult to reconcile with themodel in which SrcI and the nearby Becklin-Neugebauer Object were ejected froma multiple system 500 years ago.

ALMA Observations of Orion Source I at 350 and 660 GHz