Abell 3827：有星系吞食的星系团之引力透镜
Abell 3827: Cannibal Cluster Gravitational Lens
Image Credit: ESA/Hubble & NASA, R. Massey
Explanation: Is that one galaxy or three? Toward the right of the featured Hubble image of the massive galaxy cluster Abell 3827 is what appears to be a most unusual galaxy — curved and with three centers. A detailed analysis, however, finds that these are three images of the same background galaxy — and that there are at least four more images. Light we see from the single background blue galaxy takes multiple paths through the complex gravity of the cluster, just like a single distant light can take multiple paths through the stem of a wine glass. Studying how clusters like Abell 3827 and their component galaxies deflect distant light gives information about how mass and dark matter are distributed. Abell 3827 is so distant, having a redshift of 0.1, that the light we see from it left about 1.3 billion years ago — before dinosaurs roamed the Earth. Therefore, the cluster’s central galaxies have now surely all coalesced — in a feast of galactic cannibalism — into one huge galaxy near the cluster’s center.
Tomorrow’s picture: planet-forming space disk
Abell 3827：有星系吞食的星系团之引力透镜
影像提供: ESA/Hubble & NASA, R. Massey
说明: 那是一个或三个星系？在这幅以大质量星系团Abell 3827为主题的哈勃影像里，最奇特的是右侧看似有3个核心的扭曲星系。不过，经过仔细分析之后，发现它们是同一个星系的三重身影，而且视野里至少还有其他的4个身影。我们所见源自单一个泛蓝背景星系的光，以多个路径穿过此星系团复杂的重力环境，形成类似远处的光点沿着多重路径穿过酒杯脚的景观。研究像星系团Abell 3827及其成员星系这类的天体如何偏折远方的光，可据之找出其内的质量和暗物质如何分布的资讯。红移0.1的Abell 3827是如此之遥远，我们所见来自它的光，在13亿年前、远在恐龙漫游于地球上之前即已启程。也因此，这个星系团中心的星系，应已全都经由星系吞食过程，聚合成星系中心附近的单一庞大星系。
明日的图片: planet-forming space disk
