2026年1月4日
The Einstein Cross Gravitational Lens
Image Credit & License: NSF, NOIRLab, AURA, WIYN; Processing: J. Rhoads (Arizona State U.) et al.
Explanation: Most galaxies have a single nucleus — does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.
Almost Hyperspace: Random APOD Generator
Tomorrow’s picture: box star
爱因斯坦十字架引力透镜
影像提供与授权: NSF, NOIRLab, AURA, WIYN; 影像处理: J. Rhoads (Arizona State U.) et al.
说明: 大多数星系只有一个星系核，那么这个星系有四个吗？这个奇特的答案让天文学家得出结论：周围星系的星系核甚至在这张影像中根本看不见。中央的四叶草其实是背景类星体发出的光。可见的前景星系的引力场将来自这个遥远类星体的光线分解成四个不同的影像。中央的四叶草形状其实是是背景类星体发出的光。可见的前景星系之引力场折射了来自这个遥远类星体的光，形成四个不同的影像。要形成这样的海市蜃楼，类星体必须正确对齐在一个大质量星系的中心后方。这种现象被称为引力透镜效应，而这个例子被称为爱因斯坦十字架。更奇怪的是，爱因斯坦十字架的影像在相对亮度上会发生变化，有时前景星系中特定恒星的额外引力微透镜效应会增强亮度。
