Tuthill P G, Monnier J D, Danchi W C
Astronomy Department, School of Physics, University of Sydney, NSW, Australia.
Nature. 2001 Feb 22;409(6823):1012-4. doi: 10.1038/35059014.
A star forms when a cloud of dust and gas collapses. It is generally believed that this collapse first produces a flattened rotating disk, through which matter is fed onto the embryonic star at the centre of the disk. When the temperature and density at the centre of the star pass a critical threshold, thermonuclear fusion begins. The remaining disk, which can still contain up to 0.3 times the mass of the star, is then sculpted and eventually dissipated by the radiation and wind from the newborn star. But this picture of the structure and evolution of the disk remains speculative because of the lack of morphological data of sufficient resolution and uncertainties regarding the underlying physical processes. Here we present images of a young star, LkH alpha101, in which the structure of the inner accretion disk is resolved. We find that the disk is almost face-on, with a central gap (or cavity) and a hot inner edge. The cavity is bigger than previous theoretical predictions, and we infer that the position of the inner edge is probably determined by sublimation of dust grains by direct stellar radiation, rather than by disk-reprocessing or viscous-heating processes as usually assumed.
当尘埃和气体云坍缩时，恒星便开始形成。人们普遍认为，这种坍缩首先会产生一个扁平的旋转盘，物质通过这个盘被输送到盘中心的胚胎恒星上。当恒星中心的温度和密度超过临界阈值时，热核聚变就开始了。剩余的盘，其质量仍可能高达恒星质量的0.3倍，随后会受到新生恒星的辐射和星风的塑造，最终消散。但由于缺乏足够分辨率的形态学数据以及关于潜在物理过程的不确定性，盘的结构和演化的这幅图景仍只是推测。在这里，我们展示了一颗年轻恒星LkHα101的图像，其中内吸积盘的结构得以分辨。我们发现该盘几乎是正面的，有一个中心间隙（或空洞）和一个热的内边缘。这个空洞比先前的理论预测要大，并且我们推断内边缘的位置可能是由恒星直接辐射使尘埃颗粒升华所决定的，而不是像通常所假设的那样由盘的再处理或粘性加热过程决定。
