32 research outputs found
Computer-assisted methods for molecular structure elucidation: realizing a spectroscopist's dream
First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by
gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have
assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of
1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center
of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission
ring with a diameter of 42 ± 3 Όas, which is circular and encompasses a central depression in brightness with a flux
ratio 10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and
width remaining stable over four different observations carried out in different days. Overall, the observed image is
consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in
brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to
the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic
magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 ± 0.7) à 109 Me. Our radiowave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies
and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme
limit and on a mass scale that was so far not accessible
First M87 Event Horizon Telescope Results. II. Array and Instrumentation
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (λ/D) is ~25 ÎŒas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of the EHT, detail the technology and instrumentation that enable observations, and provide measures of its performance. Meeting the EHT science objectives has required several key developments that have facilitated the robust extension of the VLBI technique to EHT observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. To meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit sâ1, exceeding those of currently operating cm-wavelength VLBI arrays by more than an order of magnitude. Associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. These efforts led to the coordination and execution of the first Global EHT observations in 2017 April, and to event-horizon-scale imaging of the supermassive black hole candidate in M87