The face-on disk around TW Hya is imaged in scattered light at 1.1 and 1.6 μm using the corona-graph in the Near Infrared Camera and Multi Object Spectrometer aboard the Hubble Space Telescope. Stellar light scattered from the optically thick dust disk is seen from 20 to 230 AU. The surface brightness declines as a power law of r~(-2.6+-0.1) between 45 and 150 AU. The scattering profile indicates that the disk is flared, not geometrically flat. The disk, while spatially unresolved in thermal radiation at 12 and 18 μm in observations from the W. M. Keck Observatory, shows amorphous and crystalline silicate emission in its spectrum. A disk with silicate grains of a radius ～ 1 μm in size in its surface layers can explain the color of the scattered light and the shape of the mid-infrared spectrum. Much larger grains in the disk interior are necessary to fit the millimeter-wave spectral energy distribution, and hence grain growth from an original interstellar size population may have occurred.
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机译：使用哈勃太空望远镜上的近红外相机和多目标光谱仪中的日冕电晕图，以1.1和1.6μm的散射光在TW Hya周围的面对磁盘成像。从光学上较厚的灰尘盘散射的恒星光从20到230 AU可见。表面亮度随着r〜（-2.6 + -0.1）的幂律在45到150 AU之间下降。散射曲线表明圆盘呈喇叭形，而不是几何平面。从W. M. Keck天文台观察到，该圆盘在空间上未解析为12和18μm的热辐射，但在其光谱中显示出非晶态和结晶态的硅酸盐发射。在表面层上具有半径约为1μm的硅酸盐晶粒的圆盘可以解释散射光的颜色和中红外光谱的形状。为了适应毫米波光谱能量分布，需要在盘内部增加更大的晶粒，因此可能发生了星际大小原始种群的晶粒长大。
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