银河系光行差, 或称为长期光行差漂移,是由于太阳系质心绕着银河系中心做轨道运动的加速度引起的视自行效应,量级大约为5\uasyr.在21世纪之前, 由于观测精度尚未达到如此高的程度, 人们很少讨论银河系光行差效应.随着甚长基线干涉(Very Long Baseline Interferometer, VLBI)在基本天文学中的广泛应用和欧洲空间局(European Space Agency, ESA)的第2代微角秒天体测量卫星\gaia的问世,该效应显得逐渐重要.由于河外源的分布不均匀, 银河系光行差效应会使得河外源天球参考架缓慢旋转,进而需要修正地球岁差参数, 其中岁差速率的改正值大约为1\uasyr.对于微角秒精度的VLBI和\gaia参考架, 银河系光行差将会引起框架扭曲,在两者的连接过程中, 也是必须考虑的系统效应.
The Galactic aberration effect, also known as the secular aberration drift, is a consequence of the centripetal acceleration of the Solar System Barycenter in the circular orbit around the Galactic center. It causes distance-independent apparent proper motions (the amplitude is about 5\uasyr) for extragalactic sources which were regarded as motionless before 21th century. As the very long baseline interferometry (VLBI) has been greatly developed and the ESA (European Space Agency) space mission \emphGaia has provided ultra high-precision astrometric data, the Galactic aberration effect has becoming important. It will cause slow spin of the reference frame due to the non-uniform distribution of extragalactic sources. Therefore systematic corrections have to be applied to the Earth rotation parameters. For the precession rate, the correction is about 1\uasyr. For the very high accurate VLBI and \emphGaia reference frames, the Galactic aberration effect will introduce small distortion which is a crucial systematic effect for the link between the two reference frames.