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Curated by RSF Research Staff

An Earth-size telescope to observe supermassive black hole

Progress on solving the mysteries of black holes are increasing rapidly recently. This long-standing goal in astrophysics could be soon achieved thanks to the close observation of the immediate environment of the black hole with a high angular resolution.  Such observations could lead to images of strong gravity effects that are expected near a black hole, and to the direct detection of dynamics near the black hole as matter orbits at near light speeds.  These observations would allow to verify Einstein theory and open a new chapter in the study of general relativity in the strong field regime.

However, the nearest supermassive black hole, Sagittarius A*, is located at the center of the Milky Way, 25,640 light years away from Earth. At this distance, classical telescopes are not precise enough to give a high-resolution image. To get the adequate resolution, we would need an Earth-size telescope. While such giant telescope is out of reach, building a virtual telescope of this size is possible thanks to an array of telescopes, and like  ALMA (Atacama Large Millimeter/submillimeter Array) or the EHT (Event Horizon Telescope). This EHT has the capability of Very Long Baseline Interferometry (VLBI) at short wavelengths, a technique based on linking radio dishes across the globe to create an Earth-sized interferometer.

The first observation of this giant virtual telescope was to measure the size of the emission regions of the supermassive black holes with the largest apparent event horizons: Sagittarius A* at the center of the Milky Way.  In both cases, the sizes match that of the predicted silhouette caused by the extreme lensing of light by the black hole.

Over the past two months, the EHT team has been working hard on processing a preliminary data set that does not yet include any data from the South Pole station. Using this data set, the team has refined the data processing pipelines that will be used to calibrate the data, and also tested many of the analysis tools that will be used to make images and search for signatures of strong gravity effects at the event horizons of supermassive black holes.

In April 2017, the EHT team put their telescope to the test for the first time. Over the course of five nights, eight dishes across the globe set their sights on Sagittarius A* capturing all the data coming from the supermassive black hole situated there. However, managing such an array of telescope is not an easy task. Even gathering the data is difficult and, the EHT team waited until last December to retrieve the long-awaited shipment of the hundred hard disk drives from the South Pole. And that’s only the beginning of this journey to build the first accurate image of a supermassive black hole. And the potential outcomes are huge for the scientific community.

The impact of black holes on the universe is huge. It’s now believed that the supermassive black holes at the center of galaxies and the galaxies they live in evolve together over cosmic times, so observing what happens near the event horizon will help us understand the universe on larger scales.

EHT Director Sheperd Doeleman

While the entire team is excited about the prospect of producing that never-before-seen image, they are also making sure to work carefully and deliberately on the data, and have, therefore, not set a date for when the results will be ready. We are closer than ever before to finally capturing an image of a black hole!

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