Greenhill L J, Gwinn C R, Schwartz C, Moran J M, Diamond P J
Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
Nature. 1998 Dec 17;396(6712):650-3. doi: 10.1038/25299.
The BN/KL region in the Orion molecular cloud is an archetype for the study of the formation of stars much more massive than the Sun. This region contains luminous young stars and protostars but, like most star-forming regions, is difficult to study in detail because of the obscuring effects of dust and gas. Our basic expectations are shaped to some extent by the present theoretical picture of star formation, the cornerstone of which is that protostars accrete gas from rotating equatorial disks and shed angular momentum by ejecting gas in bipolar outflows. The main source of the outflow in the BN/KL region may be an object known as radio source I, which is commonly believed to be surrounded by a rotating disk of molecular material. Here we report high-resolution observations of silicon monoxide (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 expected disk. A slower outflow, close to the equatorial plane of the protostellar system, extends to radii of 1,000 AU.
猎户座分子云中的BN/KL区域是研究比太阳质量大得多的恒星形成的一个典型区域。该区域包含发光的年轻恒星和原恒星，但与大多数恒星形成区域一样，由于尘埃和气体的遮挡作用，很难进行详细研究。我们的基本预期在某种程度上受到当前恒星形成理论图景的影响，其基石是原恒星从旋转的赤道盘吸积气体，并通过在双极喷流中喷射气体来释放角动量。BN/KL区域喷流的主要来源可能是一个被称为射电源I的天体，人们普遍认为它被一个分子物质旋转盘所环绕。在此，我们报告了对源I周围气体中一氧化碳（SiO）和水脉泽发射的高分辨率观测结果。我们表明，在离源60天文单位（约为太阳系大小）的范围内，该区域主要由一个锥形双极喷流主导，而不是预期的盘。一个靠近原恒星系统赤道平面的较慢喷流延伸到半径为1000天文单位处。
