ISOCAM Imaging of Comets 65P/Gunn and 46P/Wirtanen☆☆☆
ISOCAM Imaging of Comets 65P/Gunn and 46P/Wirtanen☆☆☆
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彗星 65P/Gunn 和 46P/Wirtanen 的 ISOCAM 成像☆☆☆
DOI：
10.1006/icar.1998.5944
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发表时间：
1998
期刊：
影响因子：
3.2
通讯作者：
A. Rotundi
中科院分区：
文献类型：
--
作者：
L. Colangeli;E. Bussoletti;C. Pestellini;M. Fulle;V. Mennella;P. Palumbo;A. Rotundi
摘要 在本文中，我们展示了通过宽带滤波器中的 ISOCAM 在 9.62 (LW7) 和 15.00 μm (LW3) 处获得的彗星 65P/Gunn 和 46P/Wirtanen 图像。观测分别于1996年3月23日和1996年11月9日进行。这项工作的目的是分析目标的彗发和尾尘环境。将尾部模型应用于彗星图像使我们能够得出有关灰尘喷射和动力学的几个有趣的参数。 46P/Wirtanen 的尾部相对于延长的半径矢量是对称的，并且强的各向异性表征了粉尘排放（描述粉尘喷射速度 u > − 1 2 的尺寸依赖性的功率指数的最可能值）。灰尘喷射速度的估计（对于0.1毫米大小的颗粒，从日心距离R = 2.5 AU处的14 ± 3 m s -1 到R = 2.0 AU处的23 ± 2 m s -1 ）、微分尺寸分布的功效指数（-3.5和-4之间）以及质量损失率（R = 处的1.5 ± 0.5 kg s -1 ）已获得 2.5 AU 至 2 ± 1 kg s -1 (R = 2.0 AU)。我们得出的结论是，在 2.5 到 2.0 天文单位的日心距离内，最可能的尘气比接近 1。 65P/Gunn 的尘埃尾部是强烈不对称的。拟合过程表示由参数 Φ = 110° 和倾角 I = 80° 定义的灰尘喷射锥轴。粉尘喷射速度（对于0.1毫米尺寸的颗粒，从R = 2.9 AU时的16 ± 1 m s -1 到R = 2.6 AU时的24 ± 2 m s -1 ）、微分粒径分布的功效指数（值约为-4）以及粉尘质量损失率（100至300 kg s -1 之间）。红外尾部模型确定的灰尘质量损失率取决于散射效率和颗粒温度，但与灰尘堆积密度和反照率等鲜为人知的参数无关。
Abstract In this paper we present images of Comets 65P/Gunn and 46P/Wirtanen obtained by means of ISOCAM in the broadband filters at 9.62 (LW7) and 15.00 μm (LW3). The observations were performed on 23 March 1996 and on 9 November 1996, respectively. The aim of this work is to analyze the coma and tail dust environment of the targets. The application of tail models to the comet images allowed us to derive several interesting parameters about the dust ejection and dynamics. The tail of 46P/Wirtanen is symmetric with respect to the prolonged radius vector and a strong anisotropy characterizes the dust emission (most probable value of the power index describing the size dependence of the dust ejection velocity u > − 1 2 ). Estimates of the dust ejection velocity (from 14 ± 3 m s −1 at a heliocentric distance R = 2.5 AU to 23 ± 2 m s −1 at R = 2.0 AU, for 0.1-mm-sized grains), the power index of the differential size distribution (between −3.5 and −4), and the mass loss rate (from 1.5 ± 0.5 kg s −1 at R = 2.5 AU to 2 ± 1 kg s −1 at R = 2.0 AU) have been obtained. We conclude that the most probable dust-to-gas ratio is close to one, within a heliocentric distance from 2.5 to 2.0 AU. The dust tail of 65P/Gunn is strongly asymmetric. The fitting process indicates a dust ejection cone axis defined by the argument Φ = 110° and the obliquity I = 80°. The dust ejection velocity (from 16 ± 1 m s −1 at R = 2.9 AU to 24 ± 2 m s −1 at R = 2.6 AU for 0.1-mm-sized grains), the power index of the differential size distribution (around a value of −4), and the dust mass loss rate (between 100 and 300 kg s −1 ) have been determined. Dust mass loss rates determined by IR tail models depend on the scattering efficiency and the temperature of grains, but are independent of poorly known parameters, such as dust bulk density and albedo.