Astronomy Picture of the Day——首张黑洞视界尺度照片
First Horizon-Scale Image of a Black Hole
Image Credit: Event Horizon TelescopeCollaboration
Explanation: What does a black hole looklike? To find out, radio telescopes from around the Earth coordinatedobservations of black holes with the largest known event horizons on the sky.Alone, black holes are just black, but these monster attractors are known to be surrounded by glowing gas. The first image was released yesterday and resolved the area around the black hole at the center of galaxy M87 on a scale belowthat expected for its event horizon. Pictured, the dark central region is not the event horizon,but rather the black hole's shadow the central region ofemitting gas darkened by the central black hole's gravity. The size and shapeof the shadow is determined by bright gas near the event horizon, by stronggravitational lensing deflections, and by the black hole's spin. In resolvingthis black hole's shadow, the Event Horizon Telescope (ETH) bolstered evidence that Einstein's gravity works even in extreme regions, and gave clear evidencethat M87 has a central spinning black hole of about 6 billion solar masses. The EHT is not done -- future observations will be geared toward even higherresolution, better tracking of variability, and exploring the immediatevicinity of the black hole in the center of our Milky Way Galaxy.
首张黑洞视界尺度照片
黑洞是什么样子的呢？为了找寻这个答案，地球上的射电望远镜对黑洞进行了协调观测，黑洞是天空中已知的最大事件视界。单独地说，黑洞就是黑色的，但这些吸引力巨大的宇宙怪物被炽的热气体所包围。首张黑洞照片发布于4月10日，它以低于所预期事件视界的尺度解析了位于M87星系中央的黑洞周围区域。如图所示，黑暗的中心区域不是事件视界，而是黑洞的阴影，那是因为中央区域气体发出的光被中央黑洞的引力作用吞噬了。阴影的大小和形状是由事件视界附近的明亮气体、强大的引力透镜偏转以及黑洞的自转来决定。事件视界望远镜（ETH）在解析这个黑洞阴影后，除了为爱因斯坦重力理论在极端区域下也能起作用给予了支持以外，还明确了M87的中央区域有一个质量约为太阳60亿倍的自转黑洞。但是EHT的任务还没有结束，未来的观测将朝着更高分辨率、更好跟踪变异性的方向发展，而下一个目标就是我们银河系中央黑洞。
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Astronomy Picture of the Day——月掩土星