活跃小行星（3200）法厄同的超强偏振。

Extremely strong polarization of an active asteroid (3200) Phaethon.

机构信息

Center for Computational Astrophysics, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, 181-8588, Japan.

Department of Physics and Astronomy, Seoul National University, 1 Gwanak, Seoul, 08826, Republic of Korea.

出版信息

Nat Commun. 2018 Jun 27;9(1):2486. doi: 10.1038/s41467-018-04727-2.

DOI:10.1038/s41467-018-04727-2

PMID:29950658

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC6021421/

Abstract

The near-Earth asteroid (3200) Phaethon is the parent body of the Geminid meteor stream. Phaethon is also an active asteroid with a very blue spectrum. We conducted polarimetric observations of this asteroid over a wide range of solar phase angles α during its close approach to the Earth in autumn 2016. Our observation revealed that Phaethon exhibits extremely large linear polarization: P = 50.0 ± 1.1% at α = 106.5°, and its maximum is even larger. The strong polarization implies that Phaethon's geometric albedo is lower than the current estimate obtained through radiometric observation. This possibility stems from the potential uncertainty in Phaethon's absolute magnitude. An alternative possibility is that relatively large grains (~300 μm in diameter, presumably due to extensive heating near its perihelion) dominate this asteroid's surface. In addition, the asteroid's surface porosity, if it is substantially large, can also be an effective cause of this polarization.

摘要

近地小行星（3200）法厄同是双子座流星群的母体。法厄同也是一颗活动小行星，其光谱呈非常鲜明的蓝色。我们在 2016 年秋法厄同接近地球期间，对其进行了大范围太阳相位角 α 的偏振观测。我们的观测结果表明，法厄同表现出极高的线性偏振：在 α = 106.5°时，P = 50.0 ± 1.1%，其最大值甚至更大。这种强偏振意味着法厄同的几何反照率低于目前通过辐射测量观测得到的估计值。这种可能性源于法厄同绝对星等的潜在不确定性。另一种可能性是，较大的颗粒（直径约 300 μm，可能是由于在其近日点附近受到广泛加热所致）主导了这颗小行星的表面。此外，如果小行星的表面孔隙率很大，也可能是这种偏振的有效原因。