The Fascinating Unveiling of M87* with New Data

The Event Horizon Telescope Collaboration has released new images of M87* from observations taken in April 2018, one year after the first observations in April 2017. The new observations in 2018, which feature the first participation of the Greenland Telescope, reveal a familiar, bright ring of emission of the same size as we found in 2017. This bright ring surrounds a dark central shadow, and the brightest part of the ring in 2018 has shifted by about 30º relative from 2017 to now lie in the 5 o’clock position. Credit: EHT Collaboration.

Nearly five years ago, a globe-spanning team of astronomers gave the world its first-ever glimpse of a black hole. Now the team has validated both their original findings and our understanding of black holes with a new image of the supermassive black hole M87*.

This supermassive black hole, 6.5 billion times the mass of our sun, resides at the center of the Messier 87 (M87) galaxy in the Virgo galaxy cluster, located 55 million light-years from Earth.

The new image, like the old one, was captured by the Event Horizon Telescope (EHT), an array of radio telescopes stretching across the planet. These new data, however, were gathered a year later, in 2018, and benefited from enhancements in the telescope array, notably with the inclusion of a telescope in Greenland.

EHT’s original image of M87* was important not just because it represented the first time humans had imaged a black hole, but also because the object looked the way it was supposed to look. Notably, the image showed what is known as a black-hole shadow—a dark region at the center of a glowing disk of hot matter circling the black hole. A black-hole shadow isn’t a shadow in the same sense as the one you cast when you walk outside on a sunny day. Instead, the dark region is created by the black hole’s immense gravitational field, which is so strong that light cannot escape it. Since no light leaves a black hole, it appears dark.

Additionally, that strong gravity bends light that passes near the black hole without falling into it, effectively acting like a lens. This is known as gravitational lensing, and it creates a ring of light that can be seen regardless of the angle from which the black hole is viewed. These effects were both predicted from Albert Einstein’s theory of general relativity. Because M87*’s image shows these effects, it is strong evidence that general relativity and our understanding of the physics of black holes is correct.

This new M87* image was produced with key contributions from an imaging team at Caltech, including Professor Katherine (Katie) L. Bouman, assistant professor of computing and mathematical sciences, electrical engineering, and astronomy; former Caltech Ph.D. student Nitika Yadlapalli Yurk, Ph.D.; and current Caltech postdoctoral research associate in computing and mathematical sciences Aviad Levis.

Bouman is a coordinator of the EHT Imaging Working Group and was a postdoctoral fellow at the Harvard Smithsonian Center for Astrophysics and co-lead of the EHT imaging team when the original image was published in 2019. [Read More](https://phys.org/news/2024-01-m87.html)