New images of the black hole M87* show the variations in its ring

The collaboration of Event Horizon Telescope (from the English Event Horizon Telescope, EHT), an international project with strong participation from the Institute of Astrophysics of Andalusia (IAA-CSIC), has presented a new image of M87*He supermassive black hole is located at the center of the galaxy Messier 87, based on the analysis of observations in April 2018. These observations, which also include the first-time participation of the Greenland Telescope Provide an independent data set of employees in the global EHT network in 2017.

Published in the magazine Astronomy and astrophysicsThis new analysis shows a bright ring with the same dimensions as 2017 around a dark central region corresponding to the black hole's shadow, in line with the predictions of general relativity. In this new picture, however The brightest area of ​​the ring has undergone a shift about 30 degrees compared to 2017, according to theoretical models that describe the variability of turbulent material around black holes.

“A basic requirement of science is the reproducibility of results”, mention, that Keiichi Asadaa research fellow at the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan, “and the confirmation of the ring in a completely new data set is a major milestone for our collaboration and a strong indication that we are observing the shadow of a black hole and that material orbiting it.

In 2019, the EHT released the historic first image of a black hole: M87*, a supermassive black hole at the center of the galaxy Messier 87, 55 million light-years away. Thanks to combined observations throughout 2017 using a global network of radio telescopes that function like a virtual Earth-sized telescope, the image of a bright circular ring was obtained, brighter in its southern part. Subsequent analyzes of its structure in polarized light allowed us to determine the geometry of the magnetic field and the nature of the plasma surrounding the black hole.

“The acquisition of the direct image of M87* marked a new step in the study of black holes and made it possible to carry out increasingly precise tests of general relativity based on multiple astronomical observations.”, It says Jose Luis GomezVice President of the EHT Scientific Council and Head of the EHT Group at IAA-CSIC.

José Luis Gómez, Vice President of the EHT Scientific Council @ehtelescope and head of the EHT group at IAA-CSIC @iaavlbiexplains the relevance of this new analysis of M87* pic.twitter.com/RCxqY6C0Vp

— IAA-CSIC (@iaa_csic) January 18, 2024

“Our theoretical models ensure that the properties of the material around M87* should be uncorrelated between 2017 and 2018. Therefore, continued observations of M87* will help us establish independent constraints on it.” Plasma structure and magnetic field around the black hole and will allow us to distinguish complex astrophysics from the effects of general relativity.”, Gomez adds.

The new Greenland telescope

To contribute to this exciting new science, the EHT is constantly evolving. He Greenland Telescope It first joined the EHT in 2018, just five months after completing its construction in the Arctic Circle. Likewise the radio telescope Large Millimeter Telescope (LMT) With a total area of ​​50 meters, it participated for the first time and significantly improved its sensitivity. In addition, the observations were expanded to four frequency bands around 230 GHz compared to the two frequency bands used in 2017.

“The progress of science requires constant improvement in the quality of data and analysis techniques.”, stands out Rohan DahalePhD student at the IAA-CSIC, and who contributed significantly to the new results of the EHT.

“Integrating the Greenland Telescope into the EHT network was critical to refining our images of M87* in 2018,” he explains. “More significant improvements that inspire us to continue pushing the boundaries of black hole astrophysics.”

Agreement with the general theory of relativity

The image of M87* taken in 2018 is remarkably similar to that of 2017: a bright ring of the same size and width, with a dark central area and One side of the ring is brighter than the other. One of the most striking results of this new image of M87* is the stability of the diameter of its ring compared to the 2017 data, which strongly supports the conclusion that the M87 black hole is well described by general relativity.

“The radius of a black hole depends only on its mass. “Because M87* is not accreting material at high speeds (which would increase its mass), general relativity predicts that its radius should remain virtually unchanged on human timescales, as our data confirms,” he points out. Nitika Yadlapalli YurkPostdoctoral researcher at the Jet Propulsion Laboratory in California (USA) and doctor at the California Institute of Technology.

Although the size of the black hole's shadow remained constant between 2017 and 2018, the position of the ring's brightest region changed significantly in the new 2018 data, shifting about 30 degrees counterclockwise to move toward the bottom right of the ring condition. approximately at the five o'clock position.

“We already expected this remarkable change in the structure of M87* in the first results published in April 2019,” he emphasizes. Britt JeterPostdoctoral fellow at the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan.

“Although the general theory of relativity requires the size of the ring to remain stable. Emission from the chaotic and turbulent accretion disk surrounding the black hole causes the brightest region of the ring to oscillate from side to side. “The observed amplitude of this oscillation or wobble over time will serve to test our theories about the magnetic field and plasma environment around the black hole.”

New analysis tools

The analysis of the 2018 data includes eight independent imaging and modeling techniques, including both methods used in the previous analysis of M87* in 2017 and new ones developed from it Experiences from the analysis of Sgr A*the black hole at the center of the Milky Way.

“The robustness of the obtained image is significantly improved by the variety of image reconstruction and modeling techniques used. “The consistency of image morphology demonstrated by the five mapping and three modeling methods significantly increases the reliability of our results,” says Kotaro Moriyamaone of the coordinators of the EHT Image Working Group.

“It is particularly noteworthy that members of the IAA-CSIC made important contributions to this milestone by leading or co-leading the imaging processes using four of the five different imaging techniques,” adds Moriyama.

A project in continuous expansion

In addition to 2017 and 2018, the EHT also conducted observations of M87* in 2021 and 2022 and is scheduled to observe them in the first half of 2024. Each year the EHT network has improved technically, either through the addition of new telescopes, hardware improvements, or the addition of additional observing frequencies.

“The observations of the EHT represent a significant contribution to the understanding of the physics of black holes. The expansion of the EHT will improve the quality of the images. In this sense, the IAA and other partners are examining the possible integration into the network of a new radio antenna on the Canary Islands. Research with the EHT is an essential part of the IAA-CSIC’s Severo Ochoa strategic project,” he emphasizes Antxon AlberdiMember of the EHT Collaboration and director of this institute.

Event Horizon Telescope (EHT) network. / NRAO

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe and North and South America. The goal of this international initiative is to capture images of black holes in an unprecedented level of detail by creating a virtual Earth-sized telescope. Thanks to significant international investment, the EHT combines existing telescopes with innovative systems, creating an entirely new instrument with the highest angular resolution performance ever achieved.

A global network of telescopes

The telescopes involved in the EHT are ALMA, APEX, the IRAM 30 Meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), and the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope and the Greenland Telescope (GLT). The data were correlated at the Max Planck Institute for Radio Astronomy (MPIfR) and at MIT's Haystack Observatory. The subsequent processing was carried out as part of collaboration by an international team in various institutions, with very prominent participation from the IAA.

The consortium EHT includes thirteen institutions Interested, among many other research institutes around the world, including the IAA-CSIC: the Institute of Astronomy and Astrophysics of the Academia Sinica, the University of Arizona, the University of Chicago, the East Asian Observatory, the Goethe University Frankfurt, the Institute for Millimeter Radio Astronomy, the Large Millimeter Telescope, the Max Planck Institute for Radio Astronomy, the MIT Haystack Observatory, the National Astronomical Observatory of Japan, the Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

Current photo of the EHT group of the Institute of Astrophysics of Andalusia. / IAA CSIC