Coexisting conical bipolar and equatorial outflows from a high-mass protostar

The BN/KL region in the Orion molecular cloud(1) is an archetype for the st udy of the formation of stars much more massive than the Sun(2). This regio n contains luminous young stars and protostars but, like most star-forming regions, is difficult to study in detail because of the obscuring effects o f dust and gas. Our basic expectations are shaped to some extent by the pre sent theoretical picture of star formation, the cornerstone of which is tha t protostars accrete gas from rotating equatorial disks and shed angular mo mentum by ejecting gas in bipolar outflows. The main source of the outflow in the BN/KL region(3-5) may be an object known as radio source I (ref. 6), which is commonly believed to be surrounded by a rotating disk of molecula r material(7-9). Here we report high-resolution observations of silicon mon oxide (SiO) and water maser emission from the gas surrounding source I. We show that within 60 AU of the source (about the size of the Solar System), the region is dominated by a conical bipolar outflow rather than the expect ed disk A slower outflow, close to the equatorial plane of the protostellar system, extends to radii of 1,000 AU.