爱因斯坦的引力透镜十字架

爱因斯坦的引力透镜十字架

ByNASA中文

2021年10月17日 The Einstein Cross Gravitational Lens Image Credit & License: J. Rhoads (Arizona State U.) et al., WIYN, AURA, NOIRLab, NSF 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,…

Abell 3827：有星系吞食的星系团之引力透镜

Abell 3827：有星系吞食的星系团之引力透镜

ByNASA中文

2021年8月23日 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…

当黑洞互撞

当黑洞互撞

ByNASA中文

2021年04月11日 When Black Holes Collide Video Credit & Copyright: Simulating Extreme Spacetimes Collaboration Explanation: What happens when two black holes collide? This extreme scenario occurs in the centers of many merging galaxies and multiple star systems. The featured video shows a computer animation of the final stages of such a merger, while highlighting the gravitational lensing effects that would appear on a background starfield. The black regions indicate the event horizons of the dynamic duo, while a surrounding ring of shifting background stars indicates the position of their combined Einstein ring. All background stars not only have images visible outside of this Einstein ring, but also have one or more companion images visible on the inside. Eventually the two black holes coalesce. The end stages…

天鹅座方向的天空

天鹅座方向的天空

ByNASA中文

2020年8月26日 Cygnus Skyscape Image Credit & Copyright: Alistair Symon Explanation: In brush strokes of interstellar dust and glowing hydrogen gas, this beautiful skyscape is painted across the plane of our Milky Way Galaxy near the northern end of the Great Rift and the constellation Cygnus the Swan. Composed using 22 different images and over 180 hours of image data, the widefield mosaic spans an impressive 24 degrees across the sky. Alpha star of Cygnus, bright, hot, supergiant Deneb lies near top center. Crowded with stars and luminous gas clouds Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the center of the view. The reddish glow of star forming regions NGC 7000 and IC 5070, the North America…

重力的微笑

重力的微笑

ByNASA中文

2019 October 26 Gravity’s Grin Image Credit: X-ray – NASA / CXC / J. Irwin et al. ; Optical – NASA/STScI Explanation: Albert Einstein’s general theory of relativity, published over 100 years ago, predicted the phenomenon of gravitational lensing. And that’s what gives these distant galaxies such a whimsical appearance, seen through the looking glass of X-ray and optical image data from the Chandra and Hubble space telescopes. Nicknamed the Cheshire Cat galaxy group, the group’s two large elliptical galaxies are suggestively framed by arcs. The arcs are optical images of distant background galaxies lensed by the foreground group’s total distribution of gravitational mass. Of course, that gravitational mass is dominated by dark matter. The two large elliptical “eye” galaxies represent the brightest members of…

引力透镜发现最快自旋黑洞

引力透镜发现最快自旋黑洞

ByNASA中文

通过引力透镜（gravitational lensing），来自每个类星体（quasars）的光的产生了多个它的图像。 Image credit: NASA/CXC/Univ. of Oklahoma/X. Dai et al. 就像海洋中的漩涡一样，宇宙中旋转的黑洞在它们周围形成一波“洪流”。不同的是，黑洞将产生的气体尘埃盘加热到数亿度而发出高能X射线。 利用NASA钱德拉X射线天文台（Chandra X-ray Observatory）的数据和一些星系的位置巧合，天文学家采用“引力透镜”来测量五个超大质量黑洞（supermassive black holes）的自旋（spin）。其中一个黑洞周围物质的旋转速度大于光速的70％左右。 引力透镜是一种自然现象。正如爱因斯坦所预测的那样，大质量物体（比如大星系）会使周围的时空弯曲，当它正好在我们与观测目标之间时，它强大的引力会弯曲来自目标的光，从而放大并产生多个目标的图像。 在这项新研究中，天文学家使用钱德拉和引力透镜来研究六个类星体，每个类星体都有一个超大质量黑洞在快速“吞噬”周围吸积盘（accretion disk）中的物质。通过这些“介入”的透镜星系，来自每个类星体的光都通过引力透镜产生了多个图像。多亏了钱德拉卓越的成像能力，这些透镜图像得以分离。 研究人员在这项研究中取得的关键进展是他们利用了“微透镜（microlensing）”：透镜星系中的各个恒星提供了额外的放大效果。更高的放大率意味着产生X射线的区域实际上更小。 比起不旋转的黑洞，旋转的黑洞在其周围拖动空间，使物质绕黑洞的轨道更小。利用这个特性，作者从他们的微透镜分析中得出结论：紧密的轨道对应较小的X射线发射区域，这些黑洞自转更快。 结果显示，有一个被称为“爱因斯坦十字（Einstein Cross）”的类星体，其中的黑洞正以可能的最大速率旋转。这个极限对应的事件视界（event horizon），即黑洞的“不归点”，以光速旋转，大约每小时十的十二次方米。观测目标中的另外四个黑洞平均转速大约是最大速率的一半，最后一个目标没有转速估计。 “爱因斯坦十字”的X射线来自吸积盘的一部分，面积不到事件视界的2.5倍。而对于其他四个类星体，X射线来自事件视界四到五倍大小的区域。 这些黑洞为什么转的这么快呢？研究人员认为，数十亿年来，这些超大质量黑洞很可能是从旋转方向相似的吸积盘上积累物质，而不是随机方向。就像推旋转木马一样，黑洞在吸积物质的过程中不断加快速度。 钱德拉检测到的X射线产生于吸积盘上数百万度的日冕（corona），这些X射线在吸积盘的内边缘反射，黑洞附近的强重力使反射的X射线光谱（X-ray spectrum，即不同能量X射线的分布）变形。在这项研究中，X射线光谱中看到的大量扭曲意味着盘内边缘必须靠近黑洞，这进一步证明它们必须快速旋转。 所观测的类星体距地球约88亿至109亿光年，黑洞的质量有太阳的1.6亿到5亿倍。这次结果是钱德拉用引力透镜对类星体进行过的最长观测，总曝光时间在1.7到5.4天之间。研究成果发表于7月2日的《天体物理学杂志》上，可在线获取。 有关更多钱德拉的图像、多媒体和相关材料， 请访问：http://www.nasa.gov/chandra 参考： https://www.nasa.gov/mission_pages/chandra/images/x-rays-spot-spinning-black-holes-across-cosmic-sea.html