Ices on (90377) Sedna:: confirmation and compositional constraints
Ices on (90377) Sedna:: confirmation and compositional constraints
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DOI：
10.1051/0004-6361:20067021
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发表时间：
2007-04-01
影响因子：
6.5
通讯作者：
Stansberry, J. A.
中科院分区：
文献类型：
--
作者：
Emery, J. P.;Ore, C. M. Dalle;Stansberry, J. A.
我们报告了用斯皮策太空望远镜上的红外阵列相机（IRAC）测量了90377 Sedna在λ > 2.5 μ m处的反射率。塞德娜的轨道甚至远超柯伊伯带，它的近日点距离为76天文单位，因此从地球上看它非常暗淡，尽管它的体积相对较大。先前公布的近红外光谱显示CH4和N-2的可能特征分别接近2.3 μ m和2.15 μ m。这些冰和其他冰也表现出更强的吸收。> 2.5 μ m，为目前的工作提供动力。我们检测到Sedna在3.6和4.5 μ m处的通量，而不是5.8或8.0 μ m处的通量。测量到的IRAC通量被转换成几何反照率，并与之前的可见光和近红外光谱测量结果相结合。在3.6和4.5 μ m（相对于2.0-2.5 μ m区域）的强吸收很明显，证实了塞德娜表面存在冰。全波长范围（0.4-4.5 μ m）的光谱建模提供了进一步的限制。我们发现需要CH4来拟合新的数据点，但这些新的数据点不能用包含CH4和N-2作为唯一冰的模型来充分描述。我们认为水冰也存在。塞德娜光谱的几个特征表明，与阋神星和2005 FY9相比，塞德娜没有大气挥发性输运。
We report measurements of reflectances of 90377 Sedna at lambda > 2.5 mu m using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. Sedna orbits well beyond even the Kuiper Belt, with a perihelion distance of 76 AU, and is therefore very faint as viewed from Earth, despite its relatively large size. Previously published near-infrared spectra show possible signatures of CH4 and N-2 at similar to 2.3 and similar to 2.15 mu m, respectively. These and other ices also exhibit much stronger absorptions at. > 2.5 mu m, providing the motivation for the present work. We detected flux from Sedna at 3.6 and 4.5 mu m, but not at 5.8 or 8.0 mu m. The measured IRAC fluxes are converted to geometric albedos and combined with previous measurements of the visible and near-infrared spectra. Strong absorption at both 3.6 and 4.5 mu m (relative to the 2.0-2.5 mu m region) is readily apparent, confirming the presence of ices on the surface of Sedna. Spectral modeling of the full wavelength range (0.4-4.5 mu m) provides further constraints. We find that CH4 is required to fit the new data points, but that these new data points can not be adequately described with models containing CH4 and N-2 as the only ices. We suggest that H2O ice is also present. Several characteristics of the spectrum of Sedna suggest an absence of atmospheric volatile transport, in contrast to the large objects Eris and 2005 FY9.