The Event Horizon Telescope Experiment

事件视界望远镜（EHT）项目将使用全球射电望远镜网络，采用超长基线干涉测量（VLBI）的复杂技术来解析和成像附近两个超大质量黑洞附近的区域。其中一颗位于我们银河系中心（“SgrA*”，发音为“人马座- a星”），质量是太阳的400万倍；另一个位于5000万光年外的一个巨大星系（被称为“M87”）的中心，其测量质量是太阳的数十亿倍。这些区域将在无线电波长上成像，显示出黑洞直径的细节（“事件视界”）。对大质量黑洞的研究在天体物理学中有许多应用，并且引起了广泛的兴趣；这些天体被认为是遥远星系中最强大的活动的燃料。超大质量黑洞是爱因斯坦广义相对论的极端例子，但它们形成的实际机制仍不确定。由于黑洞的受欢迎程度，这个项目的众多公众宣传努力将吸引成千上万的公众成员。事件视界望远镜包括使用最近完成的由美国国家科学基金会资助的阿塔卡马大型毫米/亚毫米阵列（ALMA），以及世界上其他大型高精度射电望远镜。该项目将支持一个宽带VLBI相关器的组装，以处理EHT数据流（每会话5pb），在墨西哥的大型毫米望远镜（LMT）上构建VLBI系统，并开发一个强大的数据处理管道。通过这些进展，EHT将跟踪SgrA*事件视界的时变结构，并在最内层吸积流中搜索轨道不均匀性的周期性特征。对M87的观测将以研究射电响亮的AGN的喷流发射区域为目标，以明确区分喷流发生的模型，这些模型的预测与黑洞的预测明显不同。新的极化EHT数据将揭示史瓦西尺度的磁结构，为吸积模型和广义相对论磁流体动力学（MHD）模拟提供独特的约束条件。事件视界望远镜将在强引力极限下测试广义相对论（GR），作为其最终和最基本的奖励，EHT旨在探测GR预测的光子轨道（和封闭的“阴影”）的特征。此外，虽然只有少数源可能在最内层区域成像，该阵列能够以高角分辨率提供许多其他活动星系核（AGN）的结构和磁场的独特和重要的时域信息，探测喷射流出的空间区域，这是目前仪器研究很少的。这些主题都是AGN物理学工作的前沿，预期的数据有可能彻底改变我们对黑洞及其环境的理解，并极大地增强我们对喷射源形成和演化的理解。这项工作的广泛影响包括对学生和早期职业科学家进行射电天文仪器和毫米/亚毫米干涉测量的实践培训，而在这个项目中受到指导的人将具有独特的观测和硬件技能，这在ALMA时代将是无价的。所有EHT数据将提供给天文学界，这将最大限度地扩大其在国内和国际许多领域和学科的广泛天文影响。该项目包括通过《科学美国人》博客进行公众宣传，可能与史密森尼频道合作，以及天体物理中心的巡回展览。

The Event Horizon Telescope (EHT) project will use a global network of radio telescopes employing the sophisticated technique of Very Long Baseline Interferometry (VLBI) to resolve and image the regions near two nearby supermassive black holes. One in the center of our own Milky Way Galaxy ("SgrA*", pronounced "Sagittarius-A star") has a mass four million times that of our own Sun; the other, in the center of a massive galaxy 50 million light years away (known as "M87"), has a measured mass several billion times that of the Sun. These regions will be imaged at radio wavelengths, showing detail on the scale of the apparent black-hole diameter ("Event Horizon"). The study of massive black holes has many applications in astrophysics and is of great popular interest; such objects are thought to fuel the most powerful activity seen in far-distant galaxies. Supermassive black holes are extreme examples of Einstein's theory of General Relativity, but the actual mechanism by which they form remains uncertain. Because of the popularity of black holes, the numerous public outreach efforts of this project will enthrall thousands of members of the general public.The Event Horizon Telescope includes using the recently completed, NSF-funded Atacama Large Millimeter/submillimeter Array (ALMA), as well as other large, high-precision radio telescopes worldwide. This project will support assembly of a wideband VLBI correlator to process the torrent (5 Petabytes per session) of EHT data, construction of a VLBI system at the Large Millimeter Telescope (LMT) in Mexico, and development of a robust data processing pipeline. Through these developments, the EHT will track time-variable structure at the Event Horizon of SgrA*, and search for periodic signatures of orbiting inhomogeneities in the innermost accretion flow. Observations of M87 will target study of the jet-launching region of a radio-loud AGN, to cleanly distinguish between models of jet genesis whose predictions differ markedly close to the black hole. New polarimetric EHT data will reveal Schwarzschild scale magnetic structures, providing unique constraints on accretion models, as well as General Relativistic magneto-hydrodynamical (MHD) simulations. The Event Horizon Telescope will test General Relativity (GR) in the strong gravity limit, and as its ultimate and most fundamental prize, the EHT aims at detecting the signature of the photon orbit (and enclosed "shadow") predicted by GR. In addition, while only a few sources can potentially be imaged in the innermost regions, the array has the ability to provide unique and vital time domain information with high angular resolution on the structure and magnetic fields for many other active galactic nuclei (AGN), probing a spatial region of the jet outflow which is very poorly studied with current instrumentation. These topics are all at the forefront of work in AGN physics, and the anticipated data have the potential to revolutionize our understanding of black holes and their environments and to greatly enhance our understanding of the formation and evolution of jetted sources.Broader impacts of the work include hands-on training of students and early career scientists in radio astronomy instrumentation and mm/submm interferometry, and those mentored within this project will emerge with unique observational and hardware skills that will be invaluable in the era of ALMA. All EHT data will be made available to the astronomy community, which will maximize its broad astronomical impact across many fields and disciplines, both nationally and internationally. The project includes a public outreach effort through a Scientific American blog, a possible partnership with the Smithsonian Channel, and Center for Astrophysics' traveling exhibition.