Kalas Paul, Graham James R, Clampin Mark
Astronomy Department, University of California, Berkeley, California 94720, USA.
Nature. 2005 Jun 23;435(7045):1067-70. doi: 10.1038/nature03601.
The Sun and >15 per cent of nearby stars are surrounded by dusty disks that must be collisionally replenished by asteroids and comets, as the dust would otherwise be depleted on timescales <10(7) years (ref. 1). Theoretical studies show that the structure of a dusty disk can be modified by the gravitational influence of planets, but the observational evidence is incomplete, at least in part because maps of the thermal infrared emission from the disks have low linear resolution (35 au in the best case). Optical images provide higher resolution, but the closest examples (AU Mic and beta Pic) are edge-on, preventing the direct measurement of the azimuthal and radial disk structure that is required for fitting theoretical models of planetary perturbations. Here we report the detection of optical light reflected from the dust grains orbiting Fomalhaut (HD 216956). The system is inclined 24 degrees away from edge-on, enabling the measurement of disk structure around its entire circumference, at a linear resolution of 0.5 au. The dust is distributed in a belt 25 au wide, with a very sharp inner edge at a radial distance of 133 au, and we measure an offset of 15 au between the belt's geometric centre and Fomalhaut. Taken together, the sharp inner edge and offset demonstrate the presence of planetary-mass objects orbiting Fomalhaut.
太阳以及超过15%的邻近恒星都被尘埃盘环绕，这些尘埃盘必定是由小行星和彗星通过碰撞补充物质的，因为否则尘埃会在短于10^7年的时间尺度上耗尽（参考文献1）。理论研究表明，尘埃盘的结构会受到行星引力影响而改变，但观测证据并不完整，至少部分原因是尘埃盘热红外辐射的地图线性分辨率较低（最佳情况下为35天文单位）。光学图像提供了更高的分辨率，但最近的例子（御夫座AU Mic和绘架座β Pic）是侧视图，无法直接测量拟合行星摄动理论模型所需的方位角和径向盘结构。在此，我们报告了对从环绕北落师门（HD 216956）运行的尘埃颗粒反射的光学光的探测。该系统的倾角偏离侧视图24度，能够以0.5天文单位的线性分辨率测量其整个圆周周围的盘结构。尘埃分布在一个宽25天文单位的带中，在径向距离133天文单位处有一个非常清晰的内边缘，并且我们测量到该带的几何中心与北落师门之间有15天文单位的偏移。综合来看，清晰的内边缘和偏移表明存在环绕北落师门运行的行星质量天体。
