Understanding Black Hole Imaging Based on Very Large Baseline Interferometry (VLBI)

Abstract

In 2019, the Event Horizon Telescope made history when it captured the first known image of a blackhole. The black hole, situated in the center of the Messier 87 galaxy, is more than 55 million light-years away from earth, and was only able to be captured using Very Large Baseline Interferometry (VLBI) technology and the computational imaging technologies integrated into the Event Horizon Telescope array (The Event Horizon Telescope Collaboration, 2019). Astronomical image processing and interferometry requires the collection of radio waves using a radio telescope and analyzing that data with software. VLBI collects signals with multiple telescopes simultaneously, and the resulting data can be reduced and analyzed as data collected by a telescope with the diameter equal to the largest distance between the telescopes, thus is capable of producing an image with higher angular resolution and capturing objects further away from earth. However, due to the distance between the VLBI telescopes, algorithms are needed to fill in the hole within the collected data and reduce atmospheric noise and delays in signals (Very Long Baseline Array (VLBA)). We conduct an in depth review of the algorithm and VLBI as a whole in this paper, and hope to use our findings to further push the development of this great technology.