Institute for Astronomy, University of Hawaii, Pukalani, Maui, HI 96790, USA.
Science. 2012 Sep 28;337(6102):1638-40. doi: 10.1126/science.1223231. Epub 2012 Aug 16.
The precise shape of the Sun has not been convincingly determined, despite half a century of modern photoelectric observations. The expected deviation of the solar-limb shape from a perfect circle is very small, but such asphericity is sensitive to the Sun's otherwise invisible interior conditions, as well as the solar atmosphere. We use evidence from a long-running experiment based in space to show that, when analyzed with sufficiently high spatial resolution, the Sun's oblate shape is distinctly constant and almost completely unaffected by the solar-cycle variability seen on its surface. The solar oblateness is significantly lower than theoretical expectations by an amount that could be explained by a slower differential rotation in the outer few percent of the Sun.
尽管现代光电观测已经进行了半个世纪，但太阳的精确形状仍未得到令人信服的确定。太阳边缘形状与完美圆形的预期偏差非常小，但这种非球性对太阳内部看不见的条件以及太阳大气层非常敏感。我们利用一项长期基于太空的实验证据表明，当以足够高的空间分辨率进行分析时，太阳的扁率明显恒定，几乎不受其表面太阳活动变化的影响。太阳的扁率明显低于理论预期，这种差异可以用太阳外部百分之几的慢差速旋转来解释。
