Astronomy Picture of the Day

說明: 重力可以彎折光線。 在這張哈伯太空望遠鏡的影像裡，幾乎所有明亮的天體都是Abell 2218星系團的成員星系。 這個星系團是如此的龐大和緊湊，它的重力會彎曲和會聚後方星系的光線。 因此，這些背景星系的多重影像，會被扭曲成昏暗的拉伸弧形 - 一種類似透過一杯紅酒觀看遠方街燈的簡單透鏡效應。 Abell 2218星系團位於北天的天龍座之內，距離我們約30億光年遠。

Gravity can bend light. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into faint stretched out arcs - a simple lensing effect analogous to viewing distant street lamps through a glass of wine. The Abell 2218 cluster itself is about 3 billion light-years away in the northern constellation Draco.