Mutual events in the Cold Classical transneptunian binary system Sila and Nunam
Mutual events in the Cold Classical transneptunian binary system Sila and Nunam
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冷古典海王星双星系统 Sila 和 Nunam 中的相互事件
DOI：
10.1016/j.icarus.2012.04.014
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发表时间：
2012
期刊：
影响因子：
3.2
通讯作者：
H. Levison
中科院分区：
文献类型：
--
作者：
W. Grundy;S. Benecchi;David L. Rabinowitz;S. Porter;L. Wasserman;B. Skiff;K. Noll;A. Verbiscer;M. Buie;S. Tourtellotte;D. Stephens;H. Levison
哈勃太空望远镜在2001年至2010年间的观测，确定了冷经典跨海王星天体（79360）Sila-Nunam（暂时命名为1997 CS29）的二元成分。根据这些观测，我们确定了Nunam相对于Sila的圆形逆行互轨道，周期为12.50995±0.00036天，半长轴为2777±19公里。从地球上看，这两个亮度接近相等的天体在彼此面前交替经过，这是一个多年的相互事件季节，现在正在进行中。在2011年2月1日，两个不同的望远镜观测到一个这样的事件。相互事件季节提供了丰富的机会来更多地了解这个几乎无法分辨的双星系统，可能包括组件尺寸，颜色，形状和反照率模式。轨道的低偏心率和与轨道周期一致的光度光曲线与潮汐锁定和同步的系统一致，就像冥王星-卡戎系统一样。轨道周期和半长轴意味着系统质量为（10.84±0.22）×1018kg，结合基于斯皮策和赫歇尔热红外观测的大小估计，可以推断出平均体积密度为0.72-0.23+0.37gcm-3，与其他动力类的小型跨海王星双星的极低体积密度相当。
Hubble Space Telescope observations between 2001 and 2010 resolved the binary components of the Cold Classical transneptunian object (79360) Sila–Nunam (provisionally designated 1997 CS29). From these observations we have determined the circular, retrograde mutual orbit of Nunam relative to Sila with a period of 12.50995±0.00036days and a semimajor axis of 2777±19km. A multi-year season of mutual events, in which the two near-equal brightness bodies alternate in passing in front of one another as seen from Earth, is in progress right now, and on 2011 February 1UT, one such event was observed from two different telescopes. The mutual event season offers a rich opportunity to learn much more about this barely-resolvable binary system, potentially including component sizes, colors, shapes, and albedo patterns. The low eccentricity of the orbit and a photometric lightcurve that appears to coincide with the orbital period are consistent with a system that is tidally locked and synchronized, like the Pluto–Charon system. The orbital period and semimajor axis imply a system mass of (10.84±0.22)×1018kg, which can be combined with a size estimate based on Spitzer and Herschel thermal infrared observations to infer an average bulk density of 0.72-0.23+0.37gcm-3, comparable to the very low bulk densities estimated for small transneptunian binaries of other dynamical classes.