柯伊伯带Orcus-Vanth系统的大小、密度和形成
The size, density, and formation of the Orcus-Vanth system in the Kuiper belt
摘要：
柯伊伯带天体Orcus和它的卫星Vanth在柯伊伯带形成了一个不寻常的系统。奥库斯是柯伊伯带中已知的最大天体之一，但凡斯的相对大小要比其他大型天体的微小卫星大得多。从哈勃太空望远镜的观测中，我们发现奥库斯和凡斯有不同的可见光颜色，而且凡斯不具有奥库斯红外光谱中所见的水冰吸收特征。我们还发现，Vanth有一个近正圆轨道，周期为9.5393 +-0.0001天，半长轴为8980+-20 km，这意味着系统质量为6.32+-0.01 X 10^20 kg或矮行星Eris质量的3.8%。从斯皮策太空望远镜的观测中，我们发现热辐射与直径为940 ± 70 km、几何半径为0.28 ± 0.04的单个天体相一致。假设相同的密度和密度，这个测量意味着奥库斯和凡斯的大小分别为900和280公里，质量比为33。然而，假设非冰质的Vanth的质量比低2倍，则意味着其大小为820和640公里，质量比为2。测得的密度取决于假设的两个物体的引力比，但大约为1.5+-0.3 g cm^-3$，介于较大物体和较小物体的典型密度之间。轨道和质量比是一致的形成从一个巨大的影响和随后的外向潮汐演变，甚至与系统现在已经实现了双同步状态。该系统同样可以很好地解释，但是，由初始偏心捕获，Kozai循环，增加偏心率和减少近心的轨道的凡特，和随后的潮汐演变向内。
英文摘要：
The Kuiper belt object Orcus and its satellite Vanth form an unusual system in the Kuiper belt. Orcus is amongst the largest objects known in the Kuiper belt, but the relative size of Vanth is much larger than that of the tiny satellites of the other large objects. From Hubble Space Telescope observations we find that Orcus and Vanth have different visible colors and that Vanth does not share the water ice absorption feature seen in the infrared spectrum of Orcus. We also find that Vanth has a nearly face-on circular orbit with a period of 9.5393 +-0.0001 days and semimajor axis of 8980+-20 km, implying a system mass of 6.32+- 0.01 X 10^20 kg or 3.8% the mass of dwarf planet Eris. From Spitzer Space Telescope observations we find that the thermal emission is consistent with a single body with diameter 940+-70 km and a geometric albedo of 0.28+-0.04. Assuming equal densities and albedos, this measurements implies sizes of Orcus and Vanth of 900 and 280 km, respectively, and a mass ratio of 33. Assuming a factor of 2 lower albedo for the non-icy Vanth, however, implies sizes of 820 and 640 km and a mass ratio of 2. The measured density depends on the assumed albedo ratio of the two objects but is approximately 1.5+-0.3 g cm^-3$, midway between typical densities measured for larger and for smaller objects. The orbit and mass ratio is consistent with formation from a giant impact and subsequent outward tidal evolution and even consistent with the system having now achieved a double synchronous state. The system can equally well be explained, however, by initial eccentric capture, Kozai cycling which increases the eccentricity and decreases the pericenter of the orbit of Vanth, and subsequent tidal evolution inward.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
