Glory revealed in disk-integrated photometry of Venus
Glory revealed in disk-integrated photometry of Venus
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DOI：
10.1051/0004-6361/201423531
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发表时间：
2014-06-01
影响因子：
6.5
通讯作者：
Sanchez-Lavega, A.
中科院分区：
文献类型：
--
作者：
Garcia Munoz, A.;Perez-Hoyos, S.;Sanchez-Lavega, A.
上下文从一个空间上无法分辨的行星反射的光产生了对行星覆盖物整体光学特性的独特见解。辉光是一种光学现象，是由光在球形液滴中反向散射引起的，这些液滴的大小分布很窄;它们在地球上被称为液体云上方的局部特征。在这里，我们报告的第一个证据的荣耀，在磁盘集成测光的金星，反过来，任何行星。我们使用了以前发表的相位曲线的行星，再现了全范围的相位角与模型预测的基础上，现实的描述金星大气。我们假设行星作为一个整体的光学特性可以描述为一个统一的和稳定的云层覆盖，一个假设，同意与观测证据。我们特别表明，测量的相位曲线模拟金星上层云微米级气溶胶的散射特性，也在小相位角的荣耀发生，和荣耀的对比度是一致的光子多次散射后的预期。在光学上，行星似乎在相位角为11-13度时比完全照明时更亮;它在两者之间的相位上经历了最大的调光，最大调光率为10%。这可能意味着在系外行星的大气层中存在着球形液滴和现存的液云。一个有前景的探测将需要在小行星恒星分离的荣耀相位角精确的测光。
Context. Reflected light from a spatially unresolved planet yields unique insight into the overall optical properties of the planet cover. Glories are optical phenomena caused by light that is backscattered within spherical droplets following a narrow distribution of sizes; they are well known on Earth as localised features above liquid clouds.Aims. Here we report the first evidence for a glory in the disk-integrated photometry of Venus and, in turn, of any planet.Methods. We used previously published phase curves of the planet that were reproduced over the full range of phase angles with model predictions based on a realistic description of the Venus atmosphere. We assumed that the optical properties of the planet as a whole can be described by a uniform and stable cloud cover, an assumption that agrees well with observational evidence.Results. We specifically show that the measured phase curves mimic the scattering properties of the Venus upper-cloud micron-sized aerosols, also at the small phase angles at which the glory occurs, and that the glory contrast is consistent with what is expected after multiple scattering of photons. In the optical, the planet appears to be brighter at phase angles of similar to 11-13 degrees than at full illumination; it undergoes a maximum dimming of up to similar to 10% at phases in between.Conclusions. Glories might potentially indicate spherical droplets and, thus, extant liquid clouds in the atmospheres of exoplanets. A prospective detection will require exquisite photometry at the small planet-star separations of the glory phase angles.