爱因斯坦交叉引力透镜
(原标题: The Einstein Cross Gravitational Lens)
2021-10-17
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大多数星系只有一个核——这个星系有四个核吗？这个奇怪的答案让天文学家得出这样的结论：在这张照片中，周围星系的核心甚至都看不见。中央的三叶草是由背景类星体发出的光。可见前景星系的引力场将这个遥远类星体发出的光分解成四个不同的图像。类星体必须正确地排列在大质量星系的中心后面，这样的海市蜃楼才会很明显。一般的效应被称为引力透镜，而这种特殊的情况被称为爱因斯坦十字。更奇怪的是，爱因斯坦十字的图像在相对亮度上有所不同，偶尔会因为前景星系中特定恒星的额外引力微透镜效应而增强。
查看原文解释
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.