The Event Horizon Telescope Experiment

事件视界望远镜（EHT）项目将使用一个全球射电望远镜网络，采用甚长基线干涉测量（VLBI）的复杂技术来解析和成像两个附近超大质量黑洞附近的区域。其中一个位于我们银河系的中心（“SgrA*"，发音为“人马座-A星星”），质量是我们太阳的400万倍;另一个位于5000万光年外的大质量星系（称为“M87”）的中心，测量质量是太阳的几十亿倍。这些区域将在无线电波长下成像，显示出明显的黑洞直径尺度上的细节（“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，并引起了人们的极大兴趣;这些物体被认为是在遥远星系中看到的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然不确定。由于黑洞的普及，该项目的众多公共宣传工作将吸引成千上万的普通公众。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（阿尔马），以及世界各地的其他大型，高精度射电望远镜。该项目将支持宽带VLBI相关器的组装，以处理EHT数据的洪流（每次5 PB），在墨西哥的大型毫米波望远镜（LMT）上建造VLBI系统，并开发强大的数据处理管道。通过这些发展，EHT将跟踪SgrA* 事件视界的时变结构，并在最里面的吸积流中寻找轨道不均匀性的周期性特征。对M87的观测将针对无线电噪声活动星系核的喷气发射区域进行研究，以清楚地区分喷气成因模型，这些模型的预测在黑洞附近明显不同。新的极化EHT数据将揭示史瓦西尺度的磁性结构，为吸积模型提供独特的约束，以及广义相对论磁流体动力学（MHD）模拟。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项，EHT旨在探测光子轨道的签名此外，虽然只有少数源可以潜在地在最里面的区域中成像，该阵列能够以高角分辨率提供关于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，探测射流流出的空间区域，这是用当前仪器研究得很差的。这些课题都是活动星系核物理学研究的前沿课题，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流源形成和演化的理解。这项工作的更广泛影响包括对学生和早期职业科学家进行射电天文学仪器和毫米/亚毫米干涉测量的实践培训，而那些在这个项目中得到指导的人将获得独特的观察和硬件技能，这在阿尔马时代将是无价的。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。该项目包括通过一个科学美国人博客，与史密森尼频道和天体物理中心的巡回展览可能的合作伙伴关系的公共宣传工作。

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.