67 P/丘留莫夫-格拉西缅科彗星的尘埃轨迹
The Dust Trail of Comet 67P/Churyumov-Gerasimenko
摘要：
我们报告了2004年2月在24微米斯皮策太空望远镜拍摄的67 P/丘留莫夫-格拉西缅科彗星的尘埃尾迹和彗星核的探测结果。在2003年6月拍摄的光学帕洛玛图像中没有发现尘埃痕迹。光学和红外图像都显示出明显的颈线尾部结构，偏离了彗星的投影轨道。我们比较我们的观测模拟图像使用蒙特卡罗方法和彗星尘埃的动力学模型。我们估计这条轨迹至少有一个轨道的历史（6.6年），由尺寸>~100微米的颗粒组成。颈线是由相似大小的颗粒组成的，颗粒大小相同，但年龄较轻。总之，我们的观察和模拟表明，100微米和更大尺寸的颗粒占彗星喷射的总质量的主导地位。根据斯皮策的观测，该核的辐射有效半径为1.87 +/- 0.08公里。罗塞塔号航天器预计将于2014年抵达这颗彗星并绕其运行。假设尾迹仅由半径为1 mm的颗粒组成，我们计算出在接近和入轨过程中尾迹颗粒撞击罗塞塔号的概率很低（~10^-3）。
英文摘要：
We report the detection of comet 67P/Churyumov-Gerasimenko's dust trail and nucleus in 24 micron Spitzer Space Telescope images taken February 2004. The dust trail is not found in optical Palomar images taken June 2003. Both the optical and infrared images show a distinct neck-line tail structure, offset from the projected orbit of the comet. We compare our observations to simulated images using a Monte Carlo approach and a dynamical model for comet dust. We estimate the trail to be at least one orbit old (6.6 years) and consist of particles of size >~100 micron. The neck-line is composed of similar sized particles, particles of size but younger in age. Together, our observations and simulations suggest grains 100 micron and larger in size dominate the total mass ejected from the comet. The radiometric effective radius of the nucleus is 1.87 +/- 0.08 km, derived from the Spitzer observation. The Rosetta spacecraft is expected to arrive at and orbit this comet in 2014. Assuming the trail is comprised solely of 1 mm radius grains, we compute a low probability (~10^-3) of a trail grain impacting with Rosetta during approach and orbit insertion.
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