Polarimetric signature of the oceans as detected by near-infrared Earthshine observations
Polarimetric signature of the oceans as detected by near-infrared Earthshine observations
复制标题
近红外地球照观测检测到的海洋偏振特征
DOI：
10.1051/0004-6361/202039331
复制
发表时间：
2021
影响因子：
6.5
通讯作者：
Ishiguro M.
中科院分区：
文献类型：
--
作者：
Takahashi J.;Itoh Y.;Matsuo T.;Oasa Y.;Bach Y. P.;Ishiguro M.
发现有海洋的系外行星对寻找地外生命具有至关重要的意义。虽然地球海洋的偏振特征还没有在盘面集成的行星光中得到决定性的探测，但从理论上来说，从光滑的液体表面探测到的镜面反射光的偏振检测是可以预期的。我们的目标是探测和测量地球海洋的极化特征。方法对月球地球光照进行近红外偏振测量，采集地球光照贡献区不同海洋组分的32个夜晚数据。结果极化度与海洋分数呈显著正相关。我们发现极化的每小时变化与海洋部分的旋转转变一致。变化量与典型极化度之比可达~0.2 ~ 1.4。我们的观测为地球海洋的极化特征提供了可信的证据。近红外偏振法在寻找系外行星海洋方面可能被认为是一种有前途的技术。
ContextThe discovery of an extrasolar planet with an ocean has crucial importance in the search for life beyond Earth. The polarimetric detection of specularly reflected light from a smooth liquid surface is anticipated theoretically, though the polarimetric signature of Earth’s oceans has not yet been conclusively detected in disk-integrated planetary light.AimsWe aim to detect and measure the polarimetric signature of the Earth’s oceans.MethodsWe conducted near-infrared polarimetry for lunar Earthshine and collected data on 32 nights with a variety of ocean fractions in the Earthshine-contributing region.ResultsA clear positive correlation was revealed between the polarization degree and ocean fraction. We found hourly variations in polarization in accordance with rotational transition of the ocean fraction. The ratios of the variation to the typical polarization degree were as large as ~0.2–1.4.ConclusionsOur observations provide plausible evidence of the polarimetric signature attributed to Earth’s oceans. Near-infrared polarimetry may be considered a prospective technique in the search for exoplanetary oceans.