The interaction between the supermassive black hole at the center of the Milky Way, Sagittarius A$^*$, and its accretion disk, occasionally produces high energy flares seen in X-ray, infrared and radio. One mechanism for observed flares is the formation of compact bright regions that appear within the accretion disk and close to the event horizon. Understanding these flares can provide a window into black hole accretion processes. Although sophisticated simulations predict the formation of these flares, their structure has yet to be recovered by observations. Here we show the first three-dimensional (3D) reconstruction of an emission flare in orbit recovered from ALMA light curves observed on April 11, 2017. Our recovery results show compact bright regions at a distance of roughly 6 times the event horizon. Moreover, our recovery suggests a clockwise rotation in a low-inclination orbital plane, a result consistent with prior studies by EHT and GRAVITY collaborations. To recover this emission structure we solve a highly ill-posed tomography problem by integrating a neural 3D representation (an emergent artificial intelligence approach for 3D reconstruction) with a gravitational model for black holes. Although the recovered 3D structure is subject, and sometimes sensitive, to the model assumptions, under physically motivated choices we find that our results are stable and our approach is successful on simulated data. We anticipate that in the future, this approach could be used to analyze a richer collection of time-series data that could shed light on the mechanisms governing black hole and plasma dynamics.

翻译：位于银河系中心的人马座A*超大质量黑洞与其吸积盘之间的相互作用，偶尔会在X射线、红外和射电波段产生高能耀斑。观测到的耀斑机制之一是吸积盘内靠近视界处形成致密亮区。理解这些耀斑可为研究黑洞吸积过程提供窗口。尽管精细数值模拟预测了此类耀斑的形成，但其结构尚未被观测手段还原。本文展示了基于2017年4月11日ALMA光变曲线重构的首个轨道发射耀斑三维（3D）结构。重构结果显示，在距离视界约6倍半径处存在致密亮区。此外，重构表明在低倾角轨道平面存在顺时针旋转，这一结果与EHT和GRAVITY合作组先前的研究一致。为还原该发射结构，我们通过将神经三维表征（一种新兴的人工智能三维重构方法）与黑洞引力模型相结合，求解了一个高度病态的层析成像问题。尽管重构的三维结构受模型假设影响且有时敏感，但在物理驱动的合理选择下，我们的结果保持稳定，且该方法在模拟数据中成功验证。我们预期未来该方法可用于分析更丰富的时间序列数据，从而揭示黑洞与等离子体动力学的控制机制。