引力透镜的类型

Now that astronomers can observe lensing across the universe, they've divided such phenomena into two types: 坚强的透镜效应和弱透镜效应。强透镜是相当容易理解的-如果它可以用人眼在图像中看到的话(say, from 哈勃太空望远镜), then it's strong. Weak lensing, on the other hand, is not detectable with the naked eye. Astronomers have to use special techniques to observe and analyze the process.

由于暗物质的存在，所有遥远的星系都有一点点弱透镜。弱透镜用于探测空间中给定方向上暗物质的数量。这对天文学家来说是一个非常有用的工具，帮助他们了解宇宙中暗物质的分布。强透镜效应也使他们能够像在遥远的过去一样看到遥远的星系，这让他们很好地了解数十亿年前的情况。它还可以放大来自遥远物体的光，例如最早的星系，并经常让天文学家了解星系年轻时的活动情况。

另一种称为“微透镜效应”的透镜效应通常是由一颗恒星穿过另一颗恒星的前面，或对着更远处的物体而产生的。物体的形状可能不会扭曲，因为它具有更强的透镜效应，但光的强度会发生波动。这告诉天文学家，微透镜效应可能与此有关。有趣的是，当行星经过我们和它们的恒星之间时，它们也可能参与微透镜效应。

引力透镜效应适用于所有波长的光，从射电和红外到可见光和紫外线，这是有道理的，因为它们都是沐浴宇宙的电磁辐射光谱的一部分。

第一个引力透镜

The first gravitational lens (other than the 1919 eclipse lensing experiment) was discovered in 1979 when astronomers looked at something dubbed the "Twin QSO".QSO is shorthand for "quasi-stellar object" or quasar. Originally, these astronomers thought this object might be a pair of quasar twins. After careful observations using the Kitt Peak National Observatory in Arizona, astronomers were able to figure out that there weren't two identical quasars (distant 非常活跃的星系)在太空中彼此靠近。相反，它们实际上是一个更遥远的类星体的两张图像，当类星体的光沿着光的传播路径通过一个非常巨大的引力附近时产生。这一观察是在光学（可见光）下进行的，后来通过使用新墨西哥州的超大阵列.

爱因斯坦环

从那时起，许多引力透镜物体被发现。最著名的是爱因斯坦环，这是一种透镜状物体，其光线在透镜状物体周围形成一个“环”。当遥远的光源、透镜物体和地球上的望远镜排列在一起时，天文学家能够看到光环。这些被称为“爱因斯坦环”，当然，是因为这位科学家的工作预测了引力透镜现象而命名的。

爱因斯坦的著名十字架

Another famous lensed object is a quasar called Q2237+030, or the Einstein Cross. When the light of a quasar some 8 billion light-years from Earth passed through an oblong-shaped galaxy, it created this odd shape. Four images of the quasar appeared (a fifth image in the center is not visible to the unaided eye), creating a diamond or cross-like shape. The lensing galaxy is much closer to Earth than the quasar, at a distance of about 400 million light-years. This object has been observed several times by the 哈勃太空望远镜。

宇宙中遥远物体的强透镜效应

On a cosmic distance scale, 哈勃太空望远镜定期拍摄引力透镜的其他图像。 In many of its views, distant galaxies are smeared into arcs. Astronomers use those shapes to determine the distribution of mass in the galaxy clusters doing the lensing or to figure out their distribution of dark matter. While those galaxies are generally too faint to be easily seen, gravitational lensing makes them visible, transmitting information across billions of light-years for astronomers to study.

天文学家继续研究透镜效应，特别是当涉及黑洞时。它们强烈的引力也会折射光线，如本次模拟中使用的天空hst图像所示。